At the beginning of May, I wrote two articles about the slightly-deadened baseball’s effect on league-wide home run rates. The conclusion was pretty much exactly what you’d expect: A bouncier ball with more drag did reduce home runs, particularly among softer-hit balls at lower launch angles. In 2019, these events were the wall scrapers that barely went out of the yard. In 2021, these events are now doubles and outs, with the increase in fly outs likely contributing (at least somewhat) to baseball’s diminished run environment overall.

There were a handful of outstanding questions that I still had, one of which was the impact of the new baseball on a ballpark-by-ballpark basis. Though league-wide trends are certainly an interesting and informative way to see the effects of a new baseball on run scoring, it is also important to examine in which parks hitters are having a more difficult time getting the ball into the seats. That allows us to understand better how park effects may have been altered to different degrees as a result of MLB’s switch to the new baseball.

But it’s not just the baseball that is contributing here. MLB reportedly added humidors to five stadiums for the 2021 season, bringing the total league-wide to 10. The Rockies, Diamondbacks, Mariners, Mets, and Red Sox already had humidors in their stadiums pre-2021, but which five teams are new to that list has yet to be disclosed. We can only guess which parks now have them, but it is important to keep in mind that the ball is not the only difference.

Also important to remember when looking at ballpark-level data: The players on the home team make a huge difference in determining home run rates. It’s entirely possible that, between 2019 and ’21, a team added home run hitters to its lineup or acquired home run-adverse pitchers for its staff, or the opposite could also be true. To mitigate these effects, I only analyzed a specific slice of fly balls: those hit at an exit velocity at or above 95.0 mph, at an exit velocity below 110.0 mph, and at a launch angle below 30 degrees — the very fly balls most impacted by the new baseball in my prior analysis. I also only included fly balls hit in games on or before May 31 to control for weather effects. (That is why I am comparing 2019 to ’21.)

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Mike Shildt had a decision to make. It was only the first inning, but the Brewers were all over Daniel Ponce de Leon. They’d already scored three times, and had runners on second and third for number eight hitter Luis Urías. A hit here could break the game open, so Shildt took a risk and intentionally walked Urías. With a pitcher batting next, maybe he could salvage the inning.

There was just one problem: Daniel Ponce de Leon was pitching. His 11.6% walk rate this year has actually lowered his career mark. Not only that, but he’d already walked a batter unintentionally this inning, though it’s unclear whether that’s predictive. Either way, though, whoops:

Maybe that was a strike, and maybe it wasn’t. In any case, it turned into a run, and the game eventually turned into a Brewers rout. The Cardinals scored only three runs; as it turns out, the first inning was all Milwaukee needed. Urías didn’t have a hit on the day, not that that’s a particularly telling statistic.

Normally, I’d break down the pros and cons of Shildt’s decision in minute detail. Avoiding Urías and his career .318 OBP to face a pitcher seems good. Turning a walk into a run with Ponce de Leon on the mound seems bad. It’s certainly not a slam dunk in either direction. Read the rest of this entry »

There is a lot to dissect when it comes to understanding the increase in strikeouts in baseball. Pitchers at the plate are striking out at a higher clip than ever, but even when filtering out their plate appearances, we’re still seeing yearly increases in strikeout rate. A continued increase in velocity and an improved ability to spot fastballs up in the zone was always going to boost strikeouts, but we are also coming to shifts in pitching approach that are directly attacking long-standing hitter’s comforts, making even hitter’s counts unpredictable.

Since I’ll be going through league-wide pitching trends, it’s useful to take a quick glance at pitch usage for the year.

Fastball usage is holding steady from last year at just over 50%. In addition, the increase in slider usage continues, taking a chunk out of curveball usage. Still, the takeaway is that we’re approaching true 50/50 fastball/non-fastball usage splits over all counts, and it’s probably here to stay. Read the rest of this entry »

I’ll spare you the description of how I came up with the idea for this article. There was a lot of Alex Rodriguez’s announcing involved, and this is a family website, so my opinions on that will remain undiscussed. The point is, though, that it made me wonder about something I used to take for granted but have increasingly questioned: how do pitchers change their game plan with a runner on third base?

Depending on who you talk to, it might matter a lot or a little. Maybe pitchers won’t be willing to bounce one. Maybe they’ll pitch to a strikeout (assuming fewer than two outs), trying to keep the run from scoring. Maybe pitchers will completely ignore the runner on third and pitch normally. I’m legitimately uncertain. Not I think it’s 50% likely to be one and 50% likely to be the other — I have absolutely no idea how to weigh the relevant probabilities.

First things first; what about those bounced pitches? This is a classic announcer trope, but it’s a trope for a reason; throwing a pitch in the dirt really is more dangerous with a runner on third. Through the magic of run expectancy tables, we can see how much a one-base advancement costs the fielding team, based on whether there’s a runner on first, second, or third (I ignored other base/out states for brevity’s sake):

With no one out, everything is more or less the same; that runner on third was pretty likely to score anyway, in fact. As the outs pile up, allowing the runner from third to score hurts more and more — quite logical. Read the rest of this entry »

Last week, I laid out some broad categorizations of what makes a slider effective, when viewed in the aggregate. As a quick recap: The most important single characteristic is hitting the corners of the strike zone. If you have a slider with plus horizontal movement, it’s also okay to miss over the middle of the plate. The middle of the plate is a great location early, but a poor location late in counts. There’s more, but those were the key findings.

That analysis left some additional factors out, because there are only so many tables you can fit into an article before it all starts to look the same. Additionally, some of those factors are beyond the scope of this analysis. Sequencing and tunneling, for example, are too complex to reduce to a two-dimensional grid. Deception might be even more confusing; I’d struggle to quantify it at all, let alone simplify it into a few buckets for analysis.

Today, I’d like to look at the rest of the factors I found easy to quantify and analyze. First, let’s talk about pitch movement. Last week, I looked at horizontal movement, because that’s the classic action we associate with a slider. It’s not the only type that pitchers throw, however. Sliders are such a broad category of pitch that they encompass pitches that mostly break sideways, mostly break down (at least, relative to a fastball), or have some mixture of the two.
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Not everyone is interested in projecting the future, but one common thread in much of modern analytics in this regard is the attempt to describe a volatile thing, such as a play in baseball, using something less volatile, such as an underlying ability. This era arguably began with Voros McCracken’s DIPS research that he released 20 years ago to a wider audience than just us usenet dorks. Voros’ thesis has been modified with new information, and people tend to say (mistakenly) that he was arguing that pitchers had no control over balls in play, but DIPS and BABIP changed how we looked at pitcher/defense interaction more than any peripheral-type of number preceding it.

One of the things I want to try to project is what types of performance lead to the so-called Three True Outcomes (home run, walk, strikeout) rather than just tallying those outcomes. For example, what type of performances lead to strikeouts? I’m not just talking about velocity and stuff, but the batter-pitcher interactions at the plate — things like a pitcher’s contact percentage, which for pitchers with 100 batters faced in consecutive years from 2002 has a similar or greater r^2 to itself (0.53) than either walk rate (0.26) or strikeout rate (0.51) does. Contact rate alone has an r^2 of 0.37 when comparing it to the future strikeout rate.

As it turns out, you can explain actual strikeout rate from this synthetic estimate quite accurately, with an r^2 in the low 0.8 range.

Statcast era data works slightly better; the version of zSO which has that data is at 0.84, and the one that predates Statcast data is at 0.80. Cross-validating using repeated random subsampling (our data is limited, as there’s no “other” MLB to compare it to) yields the same results.

Like the various x measures in Statcast, these numbers shouldn’t be taken as projections in themselves. While zSO projects future strikeout rate slightly more accurately than the actual rate itself does, a mixture of both gets a better r^2 (0.59 for the sample outlined above) than either does on its own. Looking at zSO alone as a useful leading indicator, however, gives us an idea of which players may be outperforming or underperforming their strikeout rates so far this season. All numbers are through Wednesday night.

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In eight of the 12 different count-states, fouls and whiffs come with the same penalty: a strike. In a 1–1 count, for example, it really doesn’t matter whether you look silly swinging and missing at a curveball or just miss a home run by being a few inches wide of the foul pole. In either case, hitters have to come back for another swing, with the count now 1–2.

We all know this. Those are just the rules of the game. But it creates a very interesting hierarchy for hitters. When a hitter swings, only one of three things can happen: He can put the ball in play, foul it off, or whiff. And, as mentioned, for two-thirds of those outcomes — the foul and the whiff — no distinction is even made in eight of the 12 count-states. No wonder that the league-average hitter, by run value, is penalized when he swings.

But fouls have a unique property that makes them wholly different than whiffs: the ability to prolong at-bats. In the same way that you can’t lose on a serve in ping pong, you can’t strike out on a foul ball (bunts excluded). While they carry the same penalty as whiffs in all non–two-strike counts, foul balls manage to be the only safety net for hitters when their backs are against the wall, and to me, it makes for a pretty interesting dichotomy when you break it down that way.

Because foul balls provide this special safety net for hitters, it would make sense intuitively that hitters who foul off more pitches probably strike out less. If a hitter fouls off a lot of pitches, especially relative to the number of whiffs he creates, he is almost certainly going to avoid a K and eventually should get a pitch to put in play. Indeed, there is a pretty strong correlation between foul-to-whiff ratio and strikeout rate:

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What’s the most important characteristic of a slider? Let me show you a table:

There are two things that might need explaining in here. The attack zones are Baseball Savant’s way of cutting the strike zone up into granular pieces, and I think they’re neat. They look like so:

Run values are from the batter’s perspective, so that -785 runs in the shadow zone means that batters have been 785 runs below average — what they’ve done on all pitches across the whole year — when they faced sliders in the shadow zone. In other words, sliders on the corners of the plate have been excellent — not really a shock.

What’s the most important characteristic of a slider, then? Well, allow me to show you a different table:

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If you are a regular FanGraphs reader, chances are that you’re aware of the rise in strikeouts across the majors. At this point, bemoaning the rise in strikeouts is an essential component of the baseball media apparatus. Every season is accompanied by pieces on the subject. I found this type of article going as far back as 2013, and they have been especially prevalent in recent seasons. It seems to be a rite of passage to put out a piece on the increasing strikeout rate, so as a newly minted member of the baseball writing community, here is my entry in the genre.

For context, the league-wide strikeout rate has increased every season since 2005, when it sat at 16.4%. In 2021, that figure has risen to 24.1%. That is a 47% increase in 16 seasons. Not only has the strikeout percentage monotonically increased, but the rate at which it is increasing is growing. From 2005-09, the rate increased by 9.7%; from 2010-14, 10.3%. In the most recent five seasons, the strikeout rate increased by 11.6%.

The question is always who and what is driving this phenomenon, and the answer is almost always “well, there are a few factors at play.” One angle that I thought has been under-researched is hitter behavior with two strikes. You may have heard your favorite local newspaper columnist bemoan the idea that hitters do not have a two-strike approach anymore, that all they try to do is hit home runs, which has led to all the strikeouts. Of course, this type of thinking is reductive, mostly because it does not even consider the role of the pitcher. Nevertheless, many have discussed two-strike results, though more anecdotally than quantitatively. So let’s investigate this aspect of the strikeout rate problem first. The following is the strikeout rate and wOBA in plate appearances that reach two-strike counts in the Statcast era:

Like the overall strikeout rate, the strikeout rate in these plate appearances is monotonically increasing but much more slowly. Year-over-year, the increase never exceeds 2% besides this season and 2020 (about 3%). I will note we are only about a month and a half into the season and given the weather, league offense is at its nadir, so I would expect this to regress some. wOBA with two strikes has jumped in the Statcast era and this season so far has stuck out like a sore thumb. The weather caveat applies here also, as does the caveat that we are dealing with only a fraction of the plate appearances in 2021 versus all other seasons besides 2020 (for obvious reasons). This information seemingly debunks the awful two strike approach theory, at least within the defined time frame. Hitters are barely striking out more when they get to two strikes and their overall performance has not changed much season-over-season, 2021 notwithstanding. If we dig further into two strike behavior, the idea that hitters have drastically changed when they are confronted with two strikes does not track:

I will note that the chase rate calculation is based on my own filtering of the Statcast data from Baseball Savant. The swinging strike rate has increased every season and the rate at which balls are put in play with two strikes has decreased every year, which gives some credence to the complaint about hitter behavior. I would argue the changes are so small, however, that drastic claims about today’s players are not warranted. We are talking about 1.3 percentage points in terms of swinging strike rate, and 2.2 percentage points in balls in play rate from 2015-21. I do not think anyone without access to this kind of statistical information can really tell the difference between those figures when watching the game. The swing rate with two strikes has been very stable in this era. In terms of chase rate, batters have become more discerning, which can only be construed as a positive development, assuming we believe it’s better to have fewer strikeouts.

Interestingly, the rate of called strikes as a percentage of total two-strike pitches has seen a noticeable jump in 2021. Devan Fink wrote about how pitchers have become more aggressive throwing the ball in the zone this season with the advent of the new ball. I would imagine this is the impetus for the growth in the percentage of strikeouts via the called strike.

Overall, the differences in two-strike performances between seasons do not seem substantial enough to explain the acceleration of the strikeout rate growth. Maybe it is not batter performance in two strike counts, but instead a notably higher percentage of total pitches being thrown with two strikes?

There is basically no difference between 2021 and the preceding five seasons combined. The count-based run values are more of a mixed bag with no discernible trend.

Two strike performance changes does not seem notable in recent vintage. In fact, the swinging strike rates in all counts have effectively increased at the same rate across all counts.

The last thing I investigated was looking at pitch types and seeing if any groups of pitches are more responsible for the rate of whiffs than the others. Here there are more interesting trends.

Neither breaking pitches nor offspeed pitches have seen much of an influx in swinging strikes. Hitters have struggled more with fastballs, on the other hand, in all situations. (Another hat tip to Devan Fink, who wrote about the unusually large increase in fastball velocity in the month of April this season.) Pitchers’ fastballs are becoming tougher to time-up and now that they are becoming more aggressive throwing the ball in the zone, they are inducing more swinging strikes with those pitches.

The league’s two-strike approach does not seem to be having an outsized effect on the rise in strikeouts, at least in this most recent era of baseball. There are small upticks in a few relevant metrics, but more of the increase has to do with swings and misses in all counts, especially on fastballs. This count-based analysis yielded similar results to an excellent piece from Chet Gutwein here at FanGraphs. He found that not only has the league’s swinging strike rate on fastballs increased more relative to other pitch types, but fastballs high in the zone were mostly to blame due to the continuing growth of velocity and, as a consequence, spin rate.

As the league tries to address the issue of fewer balls in play now and in the future, finding a way to combat the rise in pitcher velocity should be one of the first items on the docket. The fact that pitches are moving more than ever does not appear to be as large a factor, given the changes in whiff rates on breaking and offspeed pitches. Moving the mound back, which will be implemented in the Atlantic League this season, and giving hitters more time to react seems like a good start. After parsing through the two strike data, it seems like rectifying the lack of formidable two strike approaches across the majors is not the silver bullet many believe. Digging further into the data by pitch type in all counts, the main issue is rising whiff rates on fastballs, which Chet Gutwein opined on in his own piece I referenced above. So maybe combating velocity is the elusive silver bullet? Without a relatively controlled experiment we cannot say for certain. But we can say that hitters being criticized for forgoing any semblance of a two strike approach and placing the blame on them for the rise in strikeouts is most likely a futile exercise.

Last week, I investigated something that I’ve long wondered about: are relievers particularly prone to wildness on their first batter of the game? I didn’t find much of an effect, and I also got tons of valuable feedback about further avenues for investigation. Do base/out states matter? Does handedness matter? Do intentional walks skew the data?

Aside from the last one (a definite yes), I haven’t explored all of these avenues yet. I did, however, answer another question I was curious about, one that ties into the general theme of reliever walk rates. I’ll tell you upfront that I found a confusing result, and that I’d love to hear anything I’ve missed or avenues for further investigation.

Here’s the question I’m answering: when a reliever walks the first batter he faces, what does that tell us about the rest of his appearance? All of us have seen this in practice, and we probably all know the existential dread it engenders. Great, he doesn’t have his command today. How many walks are coming up? Is the lead safe? Will the team even stay in the game long enough for a new pitcher comes in?

To explore this possibility, I examined every game thrown by a reliever since the beginning of the 2015 season. I split each reliever’s appearances into two subsets: every appearance where they unintentionally walked the first batter they faced on one hand, and every other appearance (except intentional walks, I threw those out) on the other. This gave me a sample of 1,085 relievers across more than 80,000 appearances. Read the rest of this entry »