The Astros’ facelift continues. One week after trading star outfielder Kyle Tucker to Chicago, Houston has dived into the free agent market and come up with a replacement: first baseman Christian Walker, now the beneficiary of a brand spanking new three-year, $60 million contract.

Walker didn’t establish himself as a major league starter until he was almost 30; he spent the mid-2010s stuck behind Chris Davis, Freddie Freeman, Joey Votto, and Paul Goldschmidt, in that order. But since claiming the Diamondbacks’ first base job after Goldschmidt got traded, Walker has established himself as one of the most consistent players at the position. Over the past three seasons, he’s had wRC+ marks of 122, 119, and 119, and posted WAR totals of 3.9, 3.9, and 3.0. That downturn in 2024 was informed by an oblique strain that cost Walker the month of August. If he’d played 162 games, he would’ve been right back up around 3.9 WAR again.

The former South Carolina star is 33, a bit old for a big free agent signing, especially a first baseman, and even more especially a right-handed first baseman. But he’ll be a tremendous asset to the Astros, and sorely missed by the Diamondbacks. Read the rest of this entry »

Although I was perhaps foolish to think that this past week would serve as something of an extension of the Winter Meetings, with a ton more dominoes falling, there was still a nice chunk of roster moves that rolled in. For most of this week, the significant updates to the Offseason Matrices document came on the Trades/Claims page, with the free agent moves being more complementary in nature. That is, until Friday afternoon, when Christian Walker and the Houston Astros reportedly agreed to a three-year deal. We’ll start with that move. Then, we’ll work our way through the other signings, move onto the week’s two major trades, and close with a two of the latest rumors.

Free Agent Signings

Astros Sign Christian Walker for Three Years, $60 Million

• Updated Roster Projection
• Updated Payroll Projection

Effect on the Astros

Walker gives the Astros their second new righty power bat, joining corner infielder Isaac Paredes, whom they acquired from the Cubs in exchange for Kyle Tucker. Walker will man first base, with Paredes staying at third base instead of sliding over to first, which would have happened if Houston had re-signed Alex Bregman or traded for Nolan Arenado. Walker’s signing almost definitely means that Bregman will not be returning to the Astros. If they add another starting-caliber position player, it will likely be an outfielder, and probably a lefty-hitting one.

More details of the signing are still to come. Michael Baumann will cover all that later in a more detailed write-up of the signing.

Effect on Other Teams

The Yankees were the other team most strongly connected to Walker, but they’re not without options at first base. They recently traded for Cody Bellinger (more on that move below), and while ideally he’d be their starting center fielder, he is also a capable first baseman. If they keep Bellinger in the outfield, they could sign Pete Alonso, Carlos Santana, or Paul Goldschmidt. Walker is an excellent player, but he’s far from the only first baseman available for teams looking to upgrade at the position.

Effect on Similar Players

Just because Walker matched his median contract prediction in both years and dollars, that doesn’t mean Alonso will get his median prediction of six years and $135 million. That said, Walker’s deal shows that there is a solid market for slugging first basemen. Alonso is four years younger than Walker and hits for more power, so he’ll almost certainly sign a larger deal than Walker. The question is how much money and for how many years teams are willing to commit to the 30-year-old Alonso, whose value all but exclusively comes from his bat. With Walker off the board, Alonso’s market could come into greater focus in the coming days and weeks.

Red Sox Sign Patrick Sandoval for Two Years, $18.25 Million

• Updated Roster Projection
• Updated Payroll Projection

Effect on the Red Sox

The immediate effect on the Red Sox is basically nil. Sandoval underwent Tommy John surgery in late June, making a second-half return the best-case scenario for him. Once he’s back — which could be in 2026 — he’ll join Garrett Crochet, Tanner Houck, Kutter Crawford, Brayan Bello, and Lucas Giolito, who also is currently rehabbing from elbow surgery, in Boston’s rotation mix. He’s a good depth add to an organization that’s got some other depth arms — Richard Fitts, Cooper Criswell, Quinn Priester — but is short on impact high-level prospects.

Effect on Other Teams

Because of Sandoval’s delayed impact, there was never going to be much of an onus on teams who didn’t sign him to do something in response. He was always going to be a long-term play.

Effect on Similar Players

Sandoval’s sizable two-year rehab contract is good news for other starters in a similar boat. That group includes John Means, Marco Gonzales, Wade Miley, and José Urquidy. While Sandoval is younger than all of those guys, and therefore should beat the deals they eventually sign, Means and Urquidy are plausible to earn $10 million or more on two-year contracts.

Orioles Sign Tomoyuki Sugano for One Year, $13 Million

• Ben Clemens’ Write-Up of the Deal
• Updated Roster Projection
• Updated Payroll Projection

Effect on the Orioles

The Orioles shouldn’t — and probably won’t — abandon their quest for a top-end starter just because they added the 35-year-old Sugano, even if his excellent command makes him a strong upside play despite his age. Sugano will be guaranteed a rotation spot along with Zach Eflin, Grayson Rodriguez, and in all likelihood, Dean Kremer, but there’s still room for another arm to front the quintet.

A return of Corbin Burnes can’t be ruled out until he actually signs elsewhere, but the Giants and Blue Jays are viewed as front-runners for his services. A reunion with Jack Flaherty, who was traded to Baltimore in mid-2023 before his bounce-back 2024 season with the Tigers and Dodgers, is another option the team could be considering. Or, the Orioles could go the trade route and call the Padres about Dylan Cease or the Mariners about one of their starters.

Effect on Other Teams

Sugano’s upside and reasonable price tag likely earned him widespread interest, and other older free agent starters who will sign one-year deals just don’t have the track record that Sugano had in Japan. Teams will probably have to target lesser-caliber pitchers if they’re looking for rental starters, then.

Effect on Similar Players

Max Scherzer and Justin Verlander have Hall of Fame pedigrees, so $13 million or more seems doable for them. But starters lower down the list — like Lance Lynn, Kyle Gibson, and Martín Pérez — will probably be limited to around $10 million.

Cubs Sign Carson Kelly for Two Years, $11.5 Million

• Updated Roster Projection
• Updated Payroll Projection

Effect on the Cubs

Kelly takes the Cubs out of the market for another catcher; he’ll pair with Miguel Amaya in what should be a pretty even timeshare behind the plate. They’re both just keeping the seat warm for top prospect Moises Ballesteros.

Effect on Other Teams

Kelly was the last catcher available with a chance to sign a multi-year deal, so any other moves for free-agent catchers are going to be more temporary in nature. Yasmani Grandal, James McCann, and Elias Díaz are still on the market.

Effect on Similar Players

As mentioned above, there really aren’t any similar players left on the market. Kelly’s signing was effected by the similar catchers who signed two-year deals before him: Kyle Higashioka ($13.5 million) and Travis d’Arnaud ($12 million).

Phillies Sign Max Kepler for One Year, $10 Million

• Updated Roster Projection
• Updated Payroll Projection

Effect on the Phillies

Barring a salary dump of Nick Castellanos, the Kepler signing may well finalize the Phillies’ outfield mix. Castellanos should be in the lineup just about every day, with left-handed hitters Kepler and Brandon Marsh playing mostly against righty pitchers, and Johan Rojas and Weston Wilson serving as their short-side platoon partners against left-handers.

Effect on Other Teams

There weren’t other teams in on Kepler, at least not publicly, so I don’t anticipate immediate cascading effects here. That said, with Kepler and Michael Conforto both off the board, the lefty outfielder market may start to percolate.

Effect on Similar Players

And Kepler gives those lefty outfielders another data point, along with Conforto’s $17 million price tag from the Dodgers. Lefties coming off rough years (as Kepler was) include Alex Verdugo and Jason Heyward. Meanwhile, Jesse Winker should be aiming higher than the $10 million Kepler got, considering he’s coming off a better season than the one Kepler had.

Nationals Sign Michael Soroka for One Year, $9 Million

• Updated Roster Projection
• Updated Payroll Projection

Effect on the Nationals

Soroka will reportedly return to the rotation for the Nationals, despite finishing the season on a dominant stretch out of the White Sox bullpen. MacKenzie Gore and Jake Irvin are sure to share the rotation with Soroka, with the last two spots currently coming down to a mix including (but not limited to) DJ Herz, Mitchell Parker, Cade Cavalli, Joan Adon, and Jackson Rutledge. The club may be content with that mix for now.

Effect on Other Teams

Soroka had widespread interest thanks to his excellent start to his career way back in 2019, his age (27), and his brilliance to finish the 2024 season. There aren’t exactly similar alternatives left on the market, though there are plenty of starters who will sign for right around that $9 million figure.

Effect on Similar Players

Seeing a team pay $9 million for a starter who was banished to the bullpen could be good news for other free agents who met that fate at the end of the season. However, as mentioned, those available arms don’t have the upside or traits that could translate to starting. Jakob Junis, Joe Ross, and Colin Rea are some of the pitchers who could be targeted as starters despite relieving to end the year, but none of the them brings the potential that Soroka does.

Mets Sign Griffin Canning for One Year, $4.25 Million

• Updated Roster Projection
• Updated Payroll Projection

Effect on the Mets

Canning adds to a strong stable of pitching depth for the Mets, though it’s unclear as of now if he’ll end up in the rotation or bullpen. Kodai Senga, Frankie Montas, David Peterson, and Clay Holmes are expected to make up the first four spots, leaving one or two for Canning, Paul Blackburn, Tylor Megill, José Buttó, and perhaps prospects Jonah Tong and Brandon Sproat.

Effect on Other Teams

There weren’t other teams with reported interest in Canning, so as far as we know, teams won’t be pivoting en masse now that Canning is off the market.

Effect on Similar Players

Canning got a pretty strong deal after the Braves non-tendered him; his arbitration projection was $5.4 million, per MLBTradeRumors, so getting just $1.15 million less than that isn’t too shabby. That’s good news for Cal Quantrill, the other prominent non-tendered starter. Quantrill’s arbitration projection was $9 million; considering he’s coming off a better season than Canning, he should be able to sign for something in the $5-6 million range.

White Sox Sign Bryse Wilson for One Year, $1.05 Million

• Updated Roster Projection
• Updated Payroll Projection

Effect on the White Sox

With a wide-open rotation competition after the Garrett Crochet trade, Wilson represents a new entrant. If he doesn’t win a spot there, he’ll head to the bullpen, where he’s pitched better in his career anyway.

Effect on Other Teams

Not much here. Wilson isn’t the type of player who drives the rumor mill, and while it’s fair to assume other teams were looking at him, there are plenty of other similar pitchers available.

Effect on Similar Players

Wilson is one of many pitchers who’ll sign small contracts in the coming weeks and months. This doesn’t change that.

Athletics Sign Gio Urshela for One Year ($TBA)

• Updated Roster Projection
• Updated Payroll Projection

Effect on the Athletics

Third base had been the most glaring positional need for the A’s, but they appear to have filled that hole with Urshela in the fold. The starting nine appears to be just about set, though they could always add some depth pieces.

Effect on Other Teams

The third base market was always thin beyond Alex Bregman, and it just got thinner. If you’re in need of a third baseman and don’t want to trade for one or pay for Bregman, Yoán Moncada, Josh Rojas, and Paul DeJong are just about your only choices left.

Effect on Similar Players

Urshela’s money hasn’t yet been reported, but once it is, that’ll help inform the earning potential for the above mentioned third basemen, especially because Urshela had a pretty weak season and doesn’t have much upside left at his age.

Rangers Sign Hoby Milner for One Year ($TBA)

• Updated Roster Projection
• Updated Payroll Projection

Effect on the Rangers

The Rangers’ biggest need entering the offseason was relief pitching, and Milner (plus Jacob Webb) don’t do a whole lot to help plug the leaks. Texas still needs a closer, whether that comes via a reunion with Kirby Yates or David Robertson, or a more expensive contract for Tanner Scott or Carlos Estévez.

Effect on Other Teams

Lefty relievers are always in strong supply in the offseason, but Milner offered an arm angle that’s different from most other lefties. Side-winder Tim Hill and soft-tossing Ryan Yarbrough are still available.

Effect on Similar Players

Milner’s contract could be something of a measuring stick for Hill and Yarbrough, though because Milner was non-tendered, he’s not in quite the same situation as the other two, who were free agents at the start of the offseason. Non-tenders tend to have their earnings more or less capped at what they would’ve made in arbitration, which for Milner would have been around $2.7 million.

Trades

Yankees Acquire Cody Bellinger From Cubs

• Michael Baumann’s Write-Up of the Trade
• Updated Yankees Roster Projection
• Updated Yankees Payroll Projection
• Updated Cubs Roster Projection
• Updated Cubs Payroll Projection

Where the Yankees Go From Here

You can’t replace Juan Soto, but in acquiring Bellinger, the Yankees are off to a decent start as they try to backfill the gaping hole in their lineup. Bellinger could end up playing either center field or first base for the Yankees, who entered this offseason needing to upgrade at both positions. (Yes, Aaron Judge was the best center fielder in baseball last year, but he’s better off playing a corner spot.) Bellinger’s ability to play both positions well allows the Yankees to cast a wider net looking for improvements between now and the start of the season. That’s exactly what they’re doing — look at all the players on the Matrix they’ve expressed interest in, marked in blue.

Where the Cubs Go From Here

A Bellinger trade looked like a fait accompli as soon as the Tucker trade went through, and having most of Bellinger’s money off the books will allow the Cubs to reinvest that cash into their bigger need: pitching. They could use multiple upgrades in their bullpen, and they could do that also by adding a starter, which would push Javier Assad into a relief role. With Bellinger gone, the Cubs could also use some bench depth, likely someone capable of playing third base who’ll compete with and push Matt Shaw for the job out of spring training.

Athletics Acquire Jeffrey Springs From Rays

• Eric Longenhagen’s Write-Up of the Trade
• Updated Athletics Roster Projection
• Updated Athletics Payroll Projection
• Updated Rays Roster Projection
• Updated Rays Payroll Projection

Where the Athletics Go From Here

The A’s rotation is in better shape than it was at the end of the season, with Springs and Luis Severino joining the fold, but their starting staff still lacks depth. They’ll probably keep looking to add starters, though their search will probably be limited to those in the market for cheap, short-term contracts.

Where the Rays Go From Here

The Rays were always going to deal from their surplus of starters, and Springs always made the most sense since he’s making real money by Tampa Bay’s standards. Getting a competitive balance pick (35th overall) is perhaps the big coup for the Rays here, though the electric, enigmatic Joe Boyle will certainly get a ton of attention from pitching coach Kyle Snyder. Springs may not be the last player the Rays trade away; Zack Littell, Yandy Díaz, and Brandon Lowe reportedly have all come up in trade talks.

Biggest Rumors of the Week

• Earlier this week, before the Astros signed Walker, they nearly traded for Arenado, who would’ve been a great fit for Houston’s Minute Maid Park with the Crawford Boxes in left. However, Arenado decided he’d to stay with the Cardinals — at least for now. The veteran third baseman reportedly exercised his no-trade clause and vetoed an agreed upon swap that would’ve sent him from St. Louis to Houston. According to MLB.com, Arenado is willing to accept a trade to six teams — the Red Sox, Mets, Phillies, Dodgers, Padres, and Angels — though it’s unclear if that’s a complete list. Several of those teams don’t have a spot for him anyway. Earlier today, Michael Baumann wrote about Arenado’s diminished performance and what his trade market might be. You should check that out for a more detailed look.

• In another installment of “things that didn’t actually happen,” Jeff Passan of ESPN has a good look at why the post-Soto free agency dam hasn’t really burst yet. Based on Jeff’s reporting, there’s no reason to believe we’re in for a glacially slow offseason a la 2018-19, but the remaining big moves look to be coming after Christmas.

Read the rest of this entry »

The following article is part of Jay Jaffe’s ongoing look at the candidates on the BBWAA 2025 Hall of Fame ballot. For a detailed introduction to this year’s ballot, and other candidates in the series, use the tool above; an introduction to JAWS can be found here. For a tentative schedule, and a chance to fill out a Hall of Fame ballot for our crowdsourcing project, see here. All WAR figures refer to the Baseball Reference version unless otherwise indicated.

With a foundation that centered upon the Hall of Fame triumvirate of Tom Glavine, Greg Maddux, and John Smoltz, the Braves dominated the NL West and then the NL East, reaching the postseason every year from 1991–2005 save for the ’94 strike season. Nothing lasts forever, though, and as Glavine and then Maddux departed in free agency, the team inevitably had to retool. Among the centerpieces of the next wave of Braves stars was one practically grown in their own backyard, Brian McCann.

A lefty-swinging backstop with rich baseball bloodlines, a strong arm, and a powerful bat, McCann was just 21 years old when he debuted with the Braves in June 2005. Over his first eight full seasons, he made seven All-Star teams and helped Atlanta to three postseason appearances, though the team’s success wasn’t nearly on par with the preceding dynasty. While McCann’s footwork and pitch framing wasn’t initially as polished as that of Russell Martin (who debuted with the Dodgers as a 23-year-old in 2006), he too developed into one of the game’s elite framers, that while providing stronger offense than his West Coast counterpart. Along the way, he also developed a somewhat dubious reputation as an enforcer of the unwritten rules, thanks to high-profile incidents involving José Fernández and Carlos Gómez in September 2013, though both players smoothed things over with McCann. Read the rest of this entry »

Read the rest of this entry »

I want to start off by saying that I was devastated — devastated — to learn that Nolan Arenado reportedly vetoed a trade to the Houston Astros. I guess it would’ve made some baseball sense, as Alex Bregman’s departure leaves a vacancy at third base, and new acquisition Isaac Paredes could easily slide across the diamond to first. Plus, Arenado is a three-time National League home run leader with a long history of hitting the ball in the air and to the pull side. Surely he’d find something to like about the Crawford Boxes.

But mostly, I wanted this to happen because I had a joke lined up. Read the rest of this entry »

For the 21st consecutive season, the ZiPS projection system is unleashing a full set of prognostications. For more information on the ZiPS projections, please consult this year’s introduction and MLB’s glossary entry. The team order is selected by lot, and the next team up is the Detroit Tigers.

Batters

In a year with a few surprising playoff teams, the Tigers might have the best case to be called a Cinderella story. After a June swoon dropped them nearly 10 games below .500, the Tigers looked like a team playing for 2025, to the extent that with a losing record at the trade deadline, they traded away their second-best starter, Jack Flaherty. But a funny thing happened on the way to the MLB Draft Lottery: The Tigers suddenly started winning. Going 34-19 over the final two months was just enough to squeeze into the playoffs on the season’s final weekend. While Detroit eventually lost to the Guardians in the ALDS in five games, the Tigers did prevent the Houston Astros from reaching the ALCS, the first time that’s happened since 2016.

Looking at the lineup projections, one can see a big part of why A.J. Hinch would have been my pick for AL Manager of the Year, if I had voted in that category. The Tigers basically had one good offensive performance from a full-time player on their roster: Riley Greene. To get to basically being league average in terms of runs scored, the Tigers had to juggle a lot of players of incomplete value, with lots of platoons and matchup choices, in the way that Gabe Kapler ran the 2021 San Francisco Giants — though those Giants had a much better lineup.

But when the dust clears and you look at the projections rather than the 2024 accomplishments, there’s just a lot of average here. Some of the averageness has a lot of upside; there’s a good chance that Jace Jung will be a plus major leaguer, and if he’s over his early-2024 doldrums for good, Colt Keith will be too. Parker Meadows did enough to establish himself as a viable starter in center field. Kerry Carpenter’s a great big spoon in a DH platoon. Dillon Dingler and Jake Rogers are a quietly underrated catcher tandem. But after that, there are simply a lot of questions. ZiPS has no confidence in Wenceel Pérez, and the shortstops don’t combine for a very good projection even with the computer predicting some kind of, umm, bounce back from Javier Báez. The odds that Spencer Torkelson will become a foundational part of the lineup are a lot longer than they were a year ago.

This is a team that really needs to add another impact bat. There are a variety of spots in the lineup they can target, and players like Alex Bregman and Teoscar Hernández remain on the board. This is a team that has two years left before its Cy Young-winning ace Tarik Skubal reaches free agency, a team that plays in a division that has no big dogs; this is the perfect time to make a push. This is a team that could sign Bregman and Hernández and still be tens of millions of dollars below a $200 million luxury tax number. Jung and eventually Max Clark and Thayron Liranzo all project to be contributors in the majors, but 2025-2026 are too soon to realistically expect them to have star-level breakouts. There’s work to be done here.

Pitchers

Skubal projects as the best pitcher in the majors, so that’s a nice place to start. ZiPS is widely a believer in the rest of the rotation’s abilities, but not so much the rest of the rotation’s attendance. There’s a lot of injury risk in Alex Cobb, Casey Mize, and Reese Olson, and even Skubal’s just over a year removed from serious injury. Olson and Cobb both project with ERAs below four, Mize isn’t that far off, and Jackson Jobe, Keider Montero, and Matt Manning all project as legitimate starters in the majors. But how many innings will they get from this crew? That was a question that Hinch had to answer back in October, and he answered it by basically relying on Skubal and having the bullpen construct a Potemkin rotation behind him. That’s not a formula that can be repeated over 162 games. Maybe other needs and the possibility of extending Skubal prevent the Tigers from going after Corbin Burnes or pursuing a Flaherty reunion, but this is a team that just begs for a middling inning-eater. Kyle Gibson anyone? Really, the Tigers should give Justin Verlander the hard sell on one last season in Detroit to cap off his Hall of Fame career.

The bullpen, of course, projects to be terrific. What a change from a few years ago! The front four of Beau Brieske, Jason Foley, Tyler Holton, and Will Vest project to be as dominating a quartet as you’ll find right now, and Alex Lange will join them at some point later in the season, depending on his progress recovering from lat surgery. ZiPS also has a surprising fancy for Brant Hurter as a reliever. The only pitcher in the pen that the projections actually hate is Kenta Maeda, who struggled in 2024 before being exiled to the bullpen, where he was more passable. Given the work to be done elsewhere, I’m not sure the Tigers need to do much with the relievers but wish them a good holiday and look forward to their February return.

Right now, ZiPS projects the Tigers to be about a .500 team. A .500 team with some upside is a team to take seriously in the AL Central, and there’s still the theoretical possibility that the Tigers do more this winter.

Ballpark graphic courtesy Eephus League. Depth charts constructed by way of those listed here. Size of player names is very roughly proportional to Depth Chart playing time. The final team projections may differ considerably from our Depth Chart playing time.

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Players are listed with their most recent teams wherever possible. This includes players who are unsigned or have retired, players who will miss 2025 due to injury, and players who were released in 2024. So yes, if you see Joe Schmoe, who quit baseball back in August to form a Norwegian Ukulele Dixieland Jazz band that only covers songs by The Smiths, he’s still listed here intentionally. ZiPS is assuming a league with an ERA of 4.11.

Hitters are ranked by zWAR, which is to say, WAR values as calculated by me, Dan Szymborski, whose surname is spelled with a z. WAR values might differ slightly from those that appear in the full release of ZiPS. Finally, I will advise anyone against — and might karate chop anyone guilty of — merely adding up WAR totals on a depth chart to produce projected team WAR. It is important to remember that ZiPS is agnostic about playing time, and has no information about, for example, how quickly a team will call up a prospect or what veteran has fallen into disfavor.

As always, incorrect projections are either caused by misinformation, a non-pragmatic reality, or by the skillful sabotage of our friend and former editor. You can, however, still get mad at me on Twitter or on BlueSky.

Below is an analysis of the prospects in the farm system of the Chicago Cubs. Scouting reports were compiled with information provided by industry sources as well as our own observations. This is the fifth year we’re delineating between two anticipated relief roles, the abbreviations for which you’ll see in the “position” column below: MIRP for multi-inning relief pitchers, and SIRP for single-inning relief pitchers. The ETAs listed generally correspond to the year a player has to be added to the 40-man roster to avoid being made eligible for the Rule 5 draft. Manual adjustments are made where they seem appropriate, but we use that as a rule of thumb.

A quick overview of what FV (Future Value) means can be found here. A much deeper overview can be found here.

All of the ranked prospects below also appear on The Board, a resource the site offers featuring sortable scouting information for every organization. It has more details (and updated TrackMan data from various sources) than this article and integrates every team’s list so readers can compare prospects across farm systems. It can be found here. Read the rest of this entry »

Right after FanGraphs published my piece on the Kirby Index, the metric’s namesake lost his touch. George Kirby’s trademark command — so reliable that I felt comfortable naming a statistic after him — fell off a cliff. While the walk rate remained under control, the home run rate spiked; he allowed seven home runs in May, all on pitches where he missed his target by a significant margin.

Watching the namesake of my new metric turn mediocre immediately following publication was among the many humbling experiences of publishing this story. Nevertheless, I wanted to revisit the piece. For one, it’s December. And writing the story led me down a fascinating rabbit hole: While I learned that the Kirby Index has its flaws, I also learned a ton about contemporary efforts to quantify pitcher command.

But first, what is the Kirby Index? I found that release angles, in concert with release height and width, almost perfectly predicted the location of a pitch. If these two variables told you almost everything about the location of a pitch, then a measurement of their variation for individual pitchers could theoretically provide novel information about pitcher command.

This got a few people mad on Twitter, including baseball’s eminent physicist Alan Nathan and Greg Rybarczyk, the creator of the “Hit Tracker” and a former member of the Red Sox front office. These two — particularly Rybarczyk — took issue with my use of machine learning to make these predictions, arguing that my use of machine learning suggested I didn’t understand the actual mechanics of why a pitch goes where it goes.

“You’re spot on, Alan,” wrote Rybarczyk. “The amazement that trajectory and launch parameters are strongly associated with where the ball ends up can only come from people who see tracking data as columns of digits rather than measurements of reality that reflect the underlying physics.”

While the tone was a bit much, Rybarczyk had a point. My “amazement” would have been tempered with a more thorough understanding of how Statcast calculates the location where a pitch crosses home plate. After publication, I learned that the nine-parameter fit explains why pitch location could be so powerfully predicted by release angles.

The location of a pitch is derived from the initial velocity, initial release point, and initial acceleration of the pitch in three dimensions. (These are the nine parameters.) Release angles are calculated using initial velocity and initial release point. Because the location of the pitch and the release angle are both derived from the 9P fit, it makes sense that they’d be almost perfectly correlated.

This led to a reasonable critique: If release angles are location information in a different form, why not just apply the same technique of measuring variation on the pitch locations themselves? This is a fair question. But using locations would have undermined the conclusion of that Kirby Index piece — that biomechanical data like release angles could improve the precision of command measurements.

Teams, with their access to KinaTrax data, could create their own version of the Kirby Index, not with implied release angles derived from the nine-parameter fit, but with the position of wrists and arms captured at the moment of release. The Kirby Index piece wasn’t just about creating a new way to measure command; I wanted it to point toward one specific way that the new data revolution in baseball would unfold.

But enough about that. It’s time for the leaderboards. I removed all pitchers with fewer than 500 fastballs. Here are the top 20 in the Kirby Index for the 2024 season:

And here are the bottom 20:

A few takeaways for me: First, I am so grateful Kirby got it together and finished in the top three. Death, taxes, and George Kirby throwing fastballs where he wants. Second, the top and bottom of the leaderboards are satisfying. Cody Bradford throws 89 and lives off his elite command, and Joe Boyle — well, there’s a reason the A’s threw him in as a piece in the Jeffrey Springs trade despite his otherworldly stuff. Third, there are guys on the laggard list — Seth Lugo and Miles Mikolas, in particular — who look out of place.

Mikolas lingered around the bottom of the leaderboards all year, which I found curious. Mikolas, after all, averages just 93 mph on his four-seam fastball; one would imagine such a guy would need to have elite command to remain a viable major league starter, and that league-worst command effectively would be a death sentence. Confusing this further, Mikolas avoided walks better than almost anyone.

Why Mikolas ranked so poorly in the Kirby Index while walking so few hitters could probably be the subject of its own article, but for the purposes of this story, it’s probably enough to say that the Kirby Index misses some things.

An example: Mikolas ranked second among all pitchers in arm angle variation on four-seam fastballs, suggesting that Mikolas is intentionally altering his arm angle from pitch to pitch, likely depending on whether the hitter is left-handed or right-handed. This is just one reason why someone might rank low in the Kirby Index. Another, as I mentioned in the original article, is that a pitcher like Lugo might be aiming at so many different targets that it fools a metric like the Kirby Index.

So: The Kirby Index was a fun exercise, but there are some flaws. What are the alternatives to measuring pitcher command?

Location+

Location+ is the industry standard. The FanGraphs Sabermetric library (an incredible resource, it must be said) does a great job of describing that metric, so I’d encourage you to click this hyperlink for the full description. The short version: Run values are assigned to each location and each pitch type based on the count. Each pitch is graded on the stuff-neutral locations.

Implied location value

Nobody seems particularly satisfied with Location+, including the creators of Location+ themselves. Because each count state and each pitch type uses its own run value map to distribute run value grades, it takes a super long time for the statistic to stabilize, upward of hundreds of pitches. It also isn’t particularly sticky from year to year.

The newest version of Location+, which will debut sometime in the near future, will use a similar logic to PitchProfiler’s command model. Essentially, PitchProfiler calculates a Stuff+ and a Pitching+ for each pitcher, which are set on a run value scale. By subtracting the Stuff+ run value from the Pitching+ run value, the model backs into the value a pitcher gets from their command alone.

Blobs

Whether it’s measuring the standard deviation of release angle proxies or the actual locations of the pitches themselves, this method can be defined as the “blob” method, assessing the cluster tightness of the chosen variable.

Max Bay, now a senior quantitative analyst with the Dodgers, advanced the Kirby Index method by measuring release angle “confidence ellipses,” allowing for a more elegant unification of the vertical and horizontal release angle components.

Miss distance

The central concern with the Kirby Index and all the blob methods, as I stated at the time, is the single target assumption. Ideally, instead of looking at how closely all pitchers are clustered around a single point, each pitch would be evaluated based on how close it finished to the actual target.

But targets are hard to come by. SportsVision started tracking these targets in the mid-2010s, as Eno Sarris outlined in his piece on the state of command research in 2018. These days, Driveline Baseball measures this working alongside Inside Edge. Inside Edge deploys human beings to manually tag the target location for every single pitch. With these data in hand, Driveline can do a couple of things. First, they created a Command+ model, modifying the mean miss distances by accounting for the difficulty of the target and the shape of a pitch.

Using intended zone data, Driveline also shows pitchers where exactly they should aim to account for their miss tendencies. I’m told they will be producing this methodology in a public post soon.

Catcher Targets (Computer Vision)

In a perfect world, computers would replace human beings — wait, let me try that sentence again. It is expensive and time-intensive to manually track targets through video, and so for good reason, miss target data belong to those who are willing to pay the price. Computer vision techniques present the potential to produce the data cheaply and (therefore) democratically.

Carlos Marcano and Dylan Drummey introduced their BaseballCV project in September. (Drummey was hired by the Cubs shortly thereafter.) Joseph Dattoli, the director of player development at the University of Missouri, offered a contribution to the project by demonstrating how computer vision could be used to tag catcher targets. The only limitation, Joseph pointed out, is the computing power required to comb through video of every single pitch.

There are some potential problems with any command measurement dependent on target tracking. Targets aren’t always real targets, more like cues for the pitcher to throw toward that general direction. But Joseph gets around this concern by tracking the catcher’s glove as well as his center of mass, which is less susceptible to these sorts of dekes. Still, there’s a way to go before this method scales into a form where daily leaderboards are accessible.

The Powers method

Absent a raft of public information about actual pitcher targets, there instead can be an effort to simulate them. In their 2023 presentation, “Pitch trajectory density estimation for predicting future outcomes,” Rice professor Scott Powers and his co-author Vicente Iglesias proposed a method to account for the random variation in pitch trajectories, in the process offering a framework for simulating something like a target. (I will likely butcher his methods if I try to summarize them, so I’d encourage you to watch the full presentation if you’re interested.)

The Powers method was modified by Stephen Sutton-Brown at Baseball Prospectus, who used Blake Snell as an example of the way these targeting models can be applied at scale to assess individual pitchers. First, Sutton-Brown fit a model that created a global target for each pitch type, adjusting for the count and handedness of each batter. Then, for each pitcher, this global target was tweaked to account for that pitcher’s tendencies. Using these simulated targets, he calculated their average miss distance, allowing for a separation of the run value of a pitcher’s targets from the run value of their command ability.

“Nothing”

On Twitter, I asked Lance Brozdowski what he saw as the gold standard command metric. He answered “Nothing,” which sums up the problem well. This is a challenging question, and all the existing methods have their flaws.

There are ways that the Kirby Index could be improved, but as far as I can tell, the best way forward for public command metrics is some sort of combination of the final two methods, with active monitoring of the computer vision advancements to see if consistent targets can be established.

But one would imagine the story is completely different on the team side. By marrying the KinaTrax data with miss distance information, these methods could potentially be combined to make some sort of super metric, one that I imagine gets pretty close to measuring the true command ability of major league pitchers. (In a video from Wednesday, Brozdowski reported on some of the potential of these data for measuring and improving command, as well as their limitations.) The public might not be quite there, but as far as I can tell, we’re not that far off.

Editor’s Note: This story has been updated to include Vicente Iglesias as a co-author on the 2023 presentation, “Pitch trajectory density estimation for predicting future outcomes.”