Pitcher zStats Update for the Stretch Drive

Jordan Montgomery
Jeff Curry-USA TODAY Sports

As anyone who does a lot of work with projections could likely tell you, one of the most annoying things about modeling future performance is that results themselves are a small sample size. Individual seasons, even full ones over 162 games, still feature results that are not very predictive, such as a hitter or a pitcher with a BABIP low or high enough to be practically unsustainable. For example, if Luis Arraez finishes the season hitting .333, we don’t actually know that a median projection of .333 was the correct projection going into the season. There’s no divine baseball exchequer to swoop in and let you know whether he’s “actually” a .333 hitter who did what he was supposed to, a .320 hitter who got lucky, or a .380 hitter who suffered extreme misfortune.

If you flip heads on a coin eight times out of 10 and have no reason to believe you have a special coin-flipping ability, you’ll eventually see the split approach 50/50 given a sufficiently large number of coin flips. Convergence in probability is a fairly large academic area that we thankfully do not need to go into here, but for most things in baseball, you never actually get enough coin flips to see this happen. The boundaries of a season are quite strict.

What does this have to do with projections? This volatile data becomes the source of future predictions, and one of the things done in projections is to find things that are not only as predictive as the ordinary stats but also more predictive based on fewer plate appearances or batters faced. Imagine, for example, if body mass index were a wonderful predictor of isolated power. It would be a highly useful one, as changes to it over the course of a season are bound to be rather small. The underlying reasons for performance tend to be more stable than the results, which is why ERA is more volatile than strikeout rate, and why strikeout rate is more volatile than the plate discipline stats that result in strikeout rate.

MLB’s own method comes with an x before the stat, whereas what ZiPS uses internally has a z. (I’ll let you guess what it stands for!) I’ve written more about this stuff in various other places (like here and here), so let’s get right to the data as we start the final third of the season. We’re also looking at how zStats leaders and trailers fared in the two months since I last posted the numbers. Sure, we’re using a small sample size of players and comparing a small sample size to another small sample size, but curiosity gets precedence over everything!

ZiPS HR Overachievers (June)
Name HR% (6/10) zHR% (6/10) HR% Since
José Quintana 0.9% 2.7% 2.4%
Merrill Kelly 1.1% 2.5% 2.0%
Kevin Gausman 0.8% 2.1% 1.8%
MacKenzie Gore 0.5% 2.4% 5.0%
A.J. Minter 0.0% 4.0% 2.2%
Alex Colomé 0.0% 3.7% 1.1%
Bailey Ober 1.4% 3.7%
Shane Bieber 1.5% 2.8% 2.6%
Patrick Sandoval 0.0% 1.5% 1.9%
Joel Payamps 0.0% 3.1% 6.0%
Michael Kopech 1.0% 2.5% 5.3%
Kyle Wright 1.1% 2.2% 4.2%
Zac Gallen 1.8% 3.0% 2.8%
Carlos Carrasco 1.1% 2.1% 3.9%
Taylor Hearn 3.0% 4.1% 1.8%

zHR was closer on 12 of the 14 pitchers here (Ober hasn’t pitched because of a pelvic issue). Remember that zHR doesn’t know how many homers a pitcher was projected to allow or any other standard counting numbers (strikeouts, walks, etc), so unlike a normal projection, it only knows things like how hard balls were hit, what direction/angle, swing data, etc.

ZiPS HR Overachievers
Name HR% HR zHR% zHR zHR% Diff zHR Diff
Kevin Gausman 1.2% 6 2.8% 13.5 -1.5% -7.5
Merrill Kelly 1.5% 8 2.8% 14.6 -1.3% -6.6
Alex Colomé 0.5% 1 3.8% 7.0 -3.2% -6.0
Kyle Freeland 2.4% 13 3.4% 18.8 -1.1% -5.8
Zach Jackson 0.6% 1 3.8% 6.8 -3.2% -5.8
Craig Kimbrel 0.5% 1 3.6% 6.5 -3.0% -5.5
Zach Plesac 3.0% 14 4.1% 19.2 -1.1% -5.2
José Quintana 1.7% 8 2.8% 13.2 -1.1% -5.2
Dakota Hudson 1.8% 8 3.0% 13.2 -1.2% -5.2
Patrick Sandoval 0.9% 4 2.1% 9.0 -1.2% -5.0
Ross Stripling 1.8% 6 3.3% 10.9 -1.5% -4.9
Joan Adon 2.6% 8 4.0% 12.5 -1.5% -4.5
Max Scherzer 2.2% 8 3.3% 12.4 -1.2% -4.4
Jordan Lyles 3.1% 18 3.9% 22.3 -0.8% -4.3
Taylor Hearn 2.6% 9 3.9% 13.2 -1.2% -4.2

Naturally, there are going to be a number of repeaters by simple virtue of the fact that when someone has good fortune for a couple of months, you don’t then expect them to be on the schneid for a while; the universe has no physical law of stochastic justice. Freeland is the most prominent newcomer to this list, which is concerning as a pitcher who plays in Coors Field and has never been known for punching out a lot of batters.

ZiPS HR Underachievers (June)
Name HR% (6/10) zHR% (6/10) HR% Since
Elieser Hernandez 8.3% 5.4% 0.0%
Hunter Greene 6.2% 3.7% 4.0%
Nathan Eovaldi 5.7% 3.7% 3.4%
Germán Márquez 4.3% 2.6% 3.2%
Shane McClanahan 3.2% 1.5% 2.9%
Matt Bush 5.3% 1.3% 0.0%
Caleb Smith 7.0% 3.8% 2.9%
Beau Brieske 6.7% 4.8% 1.2%
Marcus Stroman 4.0% 2.4% 3.2%
Kyle Bradish 6.0% 4.1% 2.8%
Aaron Sanchez 4.3% 2.1% 0.0%
Zack Littell 5.6% 2.3% 5.6%
Robbie Ray 4.7% 3.7% 3.1%
Marco Gonzales 4.4% 3.3% 3.1%
Lucas Giolito 4.9% 3.5% 3.1%

ZiPS was closer on 13 of 15 here, and only Littell didn’t see an improvement in his gopher ball tendencies. Hernandez has pitched in relief, been injured, and spent time in the minors, so his zero homers have been in only a handful of innings.

ZiPS HR Underachievers
Name HR% HR zHR% zHR zHR% Diff zHR Diff
Josiah Gray 6.0% 29 4.1% 19.8 1.9% 9.2
Gerrit Cole 3.8% 21 2.6% 14.3 1.2% 6.7
Hunter Greene 5.2% 23 3.7% 16.5 1.5% 6.5
Germán Márquez 3.8% 20 2.8% 14.9 1.0% 5.1
Spencer Howard 6.7% 12 3.9% 7.0 2.8% 5.0
Nathan Eovaldi 5.0% 20 3.8% 15.1 1.2% 4.9
Elieser Hernandez 7.5% 18 5.5% 13.2 2.0% 4.8
Shane McClanahan 2.9% 14 1.9% 9.2 1.0% 4.8
Colin Poche 5.8% 9 2.9% 4.5 2.9% 4.5
Jordan Montgomery 3.1% 15 2.2% 10.8 0.9% 4.2
Zach Thompson 4.0% 16 3.0% 11.9 1.0% 4.1
Corbin Burnes 3.0% 16 2.2% 11.9 0.8% 4.1
Kirk McCarty 8.2% 8 4.2% 4.1 3.9% 3.9
José Berríos 4.7% 24 4.0% 20.1 0.8% 3.9
Matt Bush 3.0% 5 0.7% 1.1 2.3% 3.9

Gray has allowed 15 homers in the last two months, but ZiPS doesn’t think that he’s deserved quite that many, shooting him to the top of the list after not appearing in June. Cole has allowed just as many over the same time period, but he’s such a dominating pitcher that it hasn’t affected his overall statistics in as obviously alarming a manner. ZiPS is increasingly hopeful about Berríos overall, and new Cardinal Montgomery debuts on this list.

ZiPS Walk Overachievers (June)
Name BB% (6/10) zBB% (6/10) BB% Since
Corbin Burnes 4.9% 7.9% 8.5%
Antonio Senzatela 4.8% 8.4% 5.9%
George Kirby 2.3% 7.3% 3.9%
Jameson Taillon 2.4% 4.9% 7.3%
Daulton Jefferies 4.7% 7.9%
Paul Blackburn 6.0% 8.3% 6.8%
Aaron Nola 3.4% 5.3% 3.7%
Craig Stammen 1.2% 7.5% 7.5%
Yimi Garcia 5.7% 11.6% 7.1%
Evan Phillips 6.7% 12.4% 7.8%
Bryan Baker 7.8% 12.6% 12.8%
Seth Lugo 5.0% 9.7% 9.9%
Cristian Javier 8.7% 11.3% 9.0%
Hunter Greene 10.0% 11.9% 8.5%
Taylor Clarke 1.1% 6.0% 6.9%

More mixed results here, with zBB only being closer on six of the 14 chances here. Where zBB was farther away from reality than actual walks in all but one case, the walk rate at least moved in the direction of zBB (which is all ZiPS expects). And I’m quite happy that the pitcher who defied zBB in a positive way was Greene, one of the more exciting raw talents among young pitchers. His ERA has slowly and steadily declined in recent months, and while it still stands inflated above five, he’s had fewer games with control lapses or home run explosions. Since June, his FIP is under four. His zBB% has improved to under 10%, and as such, he’s “graduated” from this ranking.

ZiPS Walk Overachievers
Name BB% BB zBB% zBB zBB% Diff zBB Diff
Corbin Burnes 7.1% 38 9.8% 52.4 -2.7% -14.4
Antonio Senzatela 5.3% 20 8.1% 30.6 -2.8% -10.6
Lance Lynn 4.2% 11 7.7% 20.2 -3.5% -9.2
Paul Blackburn 6.4% 30 8.4% 39.1 -1.9% -9.1
Max Fried 4.5% 25 6.1% 34.0 -1.6% -9.0
Josiah Gray 9.5% 46 11.3% 54.4 -1.7% -8.4
George Kirby 3.3% 11 5.8% 19.4 -2.5% -8.4
Taylor Clarke 4.1% 8 8.4% 16.4 -4.3% -8.4
Jameson Taillon 4.8% 24 6.4% 31.9 -1.6% -7.9
Rony Garcia 6.3% 13 10.0% 20.7 -3.7% -7.7
Craig Stammen 3.6% 5 9.2% 12.7 -5.6% -7.7
Liam Hendriks 5.7% 9 10.6% 16.6 -4.8% -7.6
Yu Darvish 4.8% 26 6.2% 33.6 -1.4% -7.6
Paolo Espino 4.1% 13 6.4% 20.5 -2.4% -7.5
Yimi Garcia 6.3% 10 11.0% 17.4 -4.7% -7.4

Burnes is having a very good season, though not one on the level of his Cy Young award-winning 2022. He’s already walked more batters than he did all of last year, and his zBB% has deteriorated further since June. White Sox fans obviously have quite a lot to be concerned about, so the idea that Lynn might be overachieving in his walk rate is probably not the analysis tidbit any are eager to hear. But there’s good news: ZiPS thinks he’s underachieving elsewhere and actually deserves a FIP of 4.32, about a third of a run better than his actual FIP of 4.63.

ZiPS Walk Underachievers (June)
Name BB% (6/10) zBB% (6/10) BB% Since
Merrill Kelly 9.9% 6.5% 4.7%
Joan Adon 13.2% 10.0% 9.1%
Sean Manaea 8.7% 6.0% 8.6%
Nick Martinez 10.5% 7.0% 6.3%
Framber Valdez 8.9% 6.4% 8.4%
Taylor Hearn 10.8% 7.7% 8.2%
Adam Wainwright 8.2% 5.6% 5.6%
Hunter Strickland 16.5% 9.9% 7.6%
Yusei Kikuchi 13.5% 10.5% 12.4%
Dillon Peters 15.4% 9.3% 1.6%
Spencer Strider 13.5% 8.9% 7.0%
Cal Quantrill 8.1% 5.7% 5.6%
Dylan Cease 12.0% 9.7% 8.5%
Daniel Lynch 9.9% 7.4% 7.2%
Aaron Ashby 11.2% 8.4% 10.2%

On this list, zBB was closer on 11 of 15 pitchers.

ZiPS Walk Underachievers
Name BB% BB zBB% zBB zBB% Diff zBB Diff
Sean Manaea 8.6% 44 6.2% 31.6 2.4% 12.4
Joely Rodríguez 15.1% 21 7.2% 10.0 7.9% 11.0
Matt Moore 12.9% 28 7.9% 17.1 5.0% 10.9
Joan Adon 12.6% 39 9.6% 29.6 3.0% 9.4
Matt Brash 16.9% 24 10.9% 15.4 6.0% 8.6
Merrill Kelly 7.4% 39 5.8% 30.5 1.6% 8.5
Aaron Ashby 10.7% 41 8.5% 32.5 2.2% 8.5
Will Smith 11.2% 21 6.8% 12.7 4.5% 8.3
Patrick Sandoval 10.6% 45 8.7% 36.9 1.9% 8.1
Caleb Smith 13.3% 29 9.6% 20.9 3.7% 8.1
Trevor Rogers 10.3% 41 8.2% 32.9 2.0% 8.1
Marco Gonzales 7.4% 40 6.0% 32.3 1.4% 7.7
Kris Bubic 11.2% 43 9.2% 35.5 2.0% 7.5
José Berríos 5.7% 29 4.3% 21.7 1.4% 7.3
Germán Márquez 8.1% 43 6.8% 35.7 1.4% 7.3

Manaea continues to befuddle ZiPS, as it just doesn’t see in the contact data why his walk rate has had a bump this season. He’s been weirdly ineffective after allowing a first-pitch ball this season, with an OPS more than 200 points higher after 1–0 than league average. One has to wonder if there’s an approach problem, something that might be fun to dig into.

ZiPS Strikeout Overachievers (June)
Name SO% (6/10) zSO% (6/10) SO% Since
Nestor Cortes 28.6% 21.8% 24.7%
Rony García 30.0% 17.8% 15.6%
Cristian Javier 30.4% 23.7% 34.2%
Frankie Montas 27.9% 23.5% 20.5%
Austin Gomber 17.9% 12.6% 17.5%
Aaron Nola 29.3% 25.2% 26.4%
Justin Verlander 27.0% 22.7% 24.2%
MacKenzie Gore 30.0% 24.5% 12.6%
Eric Lauer 27.7% 23.4% 19.7%
Joan Adon 16.5% 13.1% 25.0%
Yusei Kikuchi 25.1% 20.8% 24.8%
Carlos Rodón 30.2% 26.6% 32.1%
Eli Morgan 35.1% 25.9% 25.9%
Robert Suarez 30.9% 21.5% 0.0%
Emmanuel Clase 29.7% 20.2% 27.1%

ZiPS was closer on nine of 15, though we might as well call it eight of 14 since Suarez just got back from knee surgery and has pitched in just a couple of games. Javier and Carlos Rodón pulled the ol’ topsy-turvy trick on zSO, with their strikeout rates going in the opposite direction. zSO is still skeptical about Javier being quite this good, but it’s much less so with Rodón, as his seasonal zSO% has surged a full four percentage points since June. In other words, Rodón really has been killing it. He’s a serious Cy Young contender now, at least on my ballot (if I should vote in this award; we don’t know until September).

ZiPS Strikeout Overachievers
Name SO% SO zSO% zSO zSO% Diff zSO Diff
Spencer Strider 38.0% 138 31.1% 113.1 6.9% 24.9
Justin Steele 23.7% 106 18.4% 82.2 5.3% 23.8
Robbie Ray 28.0% 156 23.8% 132.7 4.2% 23.3
Cristian Javier 32.5% 132 27.4% 111.4 5.1% 20.6
Zac Gallen 23.9% 114 20.3% 96.6 3.6% 17.4
Nestor Cortes 26.8% 125 23.2% 108.5 3.5% 16.5
Frankie Montas 25.2% 111 21.5% 94.9 3.7% 16.1
Zack Wheeler 27.2% 137 24.1% 121.7 3.0% 15.3
Rony García 23.3% 48 16.4% 33.7 6.9% 14.3
Justin Verlander 25.7% 134 23.0% 119.8 2.7% 14.2
Yusei Kikuchi 25.0% 88 21.2% 74.6 3.8% 13.4
David Peterson 27.2% 91 23.5% 78.7 3.7% 12.3
Aaron Nola 27.9% 157 25.7% 144.7 2.2% 12.3
Sean Manaea 24.0% 122 21.6% 110.2 2.3% 11.8
Penn Murfee 30.1% 56 24.0% 44.7 6.1% 11.3

zSO is coming around on Cortes, as both his actual rate and the estimates one are much closer to converging than in June. Seeing Strider shoot to the top of this list isn’t actually concerning, as it still amounts to 11 strikeouts a game for a rookie who had one game above Double-A ball coming into the season.

ZiPS Strikeout Underachievers (June)
Name SO% (6/10) zSO% (6/10) SO% Since
Jordan Montgomery 19.4% 25.9% 20.9%
Yu Darvish 20.1% 25.8% 28.9%
Carlos Hernández 10.7% 19.7% 10.0%
Tyler Wells 15.3% 22.1% 20.2%
Noah Syndergaard 15.4% 21.6% 20.8%
Chad Kuhl 18.2% 22.8% 14.9%
Zack Greinke 11.2% 15.8% 15.6%
Kyle Hendricks 14.8% 18.8% 27.4%
Paul Blackburn 18.9% 23.0% 19.2%
Dany Jiménez 24.2% 34.4% 31.3%
Spenser Watkins 10.0% 16.5% 19.7%
Taijuan Walker 12.9% 16.9% 23.0%
Griffin Jax 26.1% 32.5% 28.4%
Steven Wilson 22.6% 31.3% 27.1%
Domingo Acevedo 20.6% 27.2% 23.3%

Nine of 15 again for zSO, though no Suarez cheats this time. I was most personally worried in June to see Greinke here, given his age and the fact that he relies less on stuff and more on moxie, knowhow, and other words used to describe every old lefty pitcher in 1934. Thankfully, the forced end of his career looks less obvious, and if you haven’t been paying too much attention to the Royals since June — and it’s perfectly OK if you haven’t — Greinke’s pitched quite well. It’s also nice to see Syndergaard match his stat — hopefully a sign that he’s slowly getting used to smiting mortals without the benefit of thunderbolts.

ZiPS Strikeout Underachievers
Name SO% SO zSO% zSO zSO% Diff zSO Diff
Jordan Montgomery 20.2% 98 26.3% 128.0 -6.2% -30.0
Tyler Wells 17.8% 68 21.5% 82.5 -3.8% -14.5
Carlos Hernández 10.7% 18 19.2% 32.5 -8.6% -14.5
Josh Winder 15.3% 29 22.9% 43.4 -7.6% -14.4
Sammy Long 18.2% 33 24.9% 45.1 -6.7% -12.1
Wandy Peralta 19.4% 34 26.3% 46.0 -6.9% -12.0
Tyler Anderson 20.1% 97 22.5% 108.5 -2.4% -11.5
Zack Greinke 13.1% 52 16.0% 63.3 -2.9% -11.3
Aaron Ashby 26.9% 103 29.8% 114.3 -2.9% -11.3
Chad Kuhl 16.5% 76 19.0% 87.3 -2.4% -11.3
Chris Bassitt 24.2% 129 26.3% 140.0 -2.1% -11.0
Domingo Acevedo 21.8% 43 27.1% 53.5 -5.3% -10.5
Spenser Watkins 15.2% 45 18.6% 55.4 -3.5% -10.4
Shane Bieber 25.4% 134 27.3% 144.2 -1.9% -10.2
Ty Blach 12.2% 21 18.1% 31.2 -5.9% -10.2

The continued presence of Montgomery dominating here is something I just don’t know how to make sense of. He’s not a pitcher who has a history of outperforming in this measurement, yet he’s more than doubling up the total of the second-place pitcher on the list. He certainly doesn’t look all that different to me, and the primary change in his pitching style this year has been a lot more sinkers (especially on strike three) than four-seamers and cutters, but in truth, none of these pitches are whiff-inducers anyway. He’s already nearly at the largest discrepancy going back to 2002 of any pitcher, the current record holder being Kevin Gausman at 34 strikeouts in 2008 (148 actual versus 182 zSO). It worked out for Gausman at least, as his strikeout rate improved from 19.1% then to 28.4% since. I hate when I don’t understand something.





Dan Szymborski is a senior writer for FanGraphs and the developer of the ZiPS projection system. He was a writer for ESPN.com from 2010-2018, a regular guest on a number of radio shows and podcasts, and a voting BBWAA member. He also maintains a terrible Twitter account at @DSzymborski.

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chazzycatmember
1 month ago

Monty’s sinker usage is way, way up this season. Maybe he’s just going for more groundballs than strikeouts?