March 25, 2023

© Bill Streicher-USA TODAY Sports

If you’re a fan of balls in play and general athleticism, I’ve got bad news for you: the 2022 playoffs have featured the highest strikeout rate in playoff history, a whopping 26.6% excluding intentional walks heading into last night’s game. More than a quarter of plate appearances have ended without the fielders moving, the runners tearing around the bases, or indeed anyone having reached at all. For what it’s worth, the unintentional walk rate is only 7%; the strikeouts are what’s out of hand, not the non-contact plays.

Why is this the case? I can think of many reasons. Maybe the teams that made the playoffs are jam-packed with the best strikeout pitchers they can find. Perhaps the parade of relievers Jay Jaffe noted last week are just too effective. Maybe that extra velocity from starters is to blame. Hitters shouldn’t escape scrutiny, either; maybe they’re swinging for the fences more with the bright lights of October on them and accepting more strikeouts as a result. It could be matchup-based, or pitchers could be using their best pitches more often. It could be better scouting of hitters’ weaknesses, or just an accident of a few pitchers getting hot, or any number of things.

If you were expecting a definitive answer, I’m afraid that’s just not the kind of analysis I feel capable of doing here. But I thought I’d at least try to rule one of these out. To me, the most obvious answer is that the batters and pitchers in the playoffs simply produce more strikeouts. To test this, I came up with a simple method: take every single batter-pitcher matchup in the postseason and predict an expected strikeout rate based on the handedness of each player and regular-season strikeout rates. What’s that, you say? That’s not simple? I agree with you – I just wanted you to be impressed by the amount of work I did.

In all honesty, it was mainly just a matter of tagging. First, I downloaded a database with every postseason plate appearance and stripped out the intentional walks. Then I downloaded a database of every player’s regular season strikeout rate, implied some normal platoon splits, and created a baseline for each matchup – right-handed pitcher against right-handed batter, for example. From there, I was able to just pull in each player’s platoon-adjusted strikeout rate for every plate appearance and use an odds ratio approximation of the expected strikeout rate of that confrontation.

That was a lot of words in a row, to the point where even my eyes glazed over while reading them. So let’s do an example. I’ll use one from the World Series: the first batter of Game 2, Framber Valdez against Kyle Schwarber. Valdez struck out 23.5% of batters he faced this year. Schwarber struck out in 30% of non-IBB plate appearances. Next, some adjustments: lefty-lefty matchups have resulted in strikeouts 5.2% more often than the average batter/pitcher confrontation. We could work out each player’s splits individually, but we’re painting with a broad brush here, so we’ll just multiply each by 1.052. That gives us an expected 24.7% strikeout rate for Valdez and 31.6% for Schwarber.

Finally, we’ll apply that odds ratio approximation. It’s just a mathematical way of stating something obvious: in a one-on-one confrontation like this, the odds of something happening depend on how likely the pitcher is to strike out a random batter, how likely the batter is to strike out against a random pitcher, and the league-average strikeout rate in their situation (lefty-lefty, 23.6%). Plug it into the formula, and you come away with a 32.8% chance of a strikeout. That makes sense. Schwarber strikes out 30% of the time against an average pitcher. Valdez strikes out more batters than the average pitcher. Knowing both those things, as well as their handedness, you’d predict a strikeout rate higher than 30%, just like the formula.

I did this for every single plate appearance of the 2022 postseason through Game 2 of the World Series, again excluding intentional walks. Using this method, I was able to arrive at an expected strikeout rate. In other words, that’s the number of strikeouts we’d expect if everyone performed exactly at their regular season rates, accounting for matchups. If that were the case, we’d have seen 841 strikeouts this postseason. In fact, we’ve seen 889. In other words, the strikeout rate is 1.4 percentage points higher than can be explained by the batters and pitchers involved alone.

I redid that calculation for each season since 2002 to see whether this excess playoff strikeout rate has always existed. In each season, I removed players who didn’t accumulate statistics in the regular season; think injuries or playoff debuts, both rare. This year doesn’t have the highest expected strikeout rate; in fact, this year’s rate is the exact average of the last seven:

Expected and Actual Postseason Strikeout Rate

Year Expected K% Actual K% Gap
2002 17.8% 16.8% -1.0%
2003 18.9% 19.1% 0.2%
2004 18.3% 16.9% -1.3%
2005 17.5% 15.8% -1.7%
2006 16.6% 15.8% -0.9%
2007 18.8% 19.7% 0.9%
2008 20.1% 19.9% -0.2%
2009 19.2% 18.8% -0.4%
2010 20.8% 23.0% 2.1%
2011 18.4% 19.2% 0.9%
2012 20.4% 21.2% 0.9%
2013 21.7% 23.3% 1.6%
2014 20.9% 19.0% -2.0%
2015 21.4% 23.1% 1.7%
2016 25.5% 24.2% -1.3%
2017 25.5% 24.3% -1.2%
2018 24.8% 23.8% -1.0%
2019 25.0% 25.8% 0.8%
2020 25.4% 25.1% -0.3%
2021 25.1% 24.5% -0.6%
2022 25.2% 26.6% 1.4%

What exactly does all of this mean? I’ll be honest with you. I’m not quite sure. If you look at the average of the past 21 years (our data for this starts in 2002, hence the cutoff), the average gap between expected strikeout rate and actual strikeout rate is near-zero; the actual strikeout rate has been 0.1 percentage points lower than expected strikeout rate, to be precise. This year has seen more strikeouts than expected, but it’s not an outlier; three other years out of the last 21 have seen a bigger gap. It certainly appears that my expected strikeout rate calculation is doing a good job of predicting playoff rates.

I suspect that a ton of minor factors come into play here. This season’s observed strikeout rate might not be the best estimation of true talent for all players; likewise, my systematically applied platoon edges aren’t perfect by any means. Painting with this broad of a brush means missing some details. Pitcher usage also matters, as does health; there are plenty of reasons that the regular season might not do the best job of predicting the postseason.

For the purposes of illustration, though, let’s compare these expected strikeout rates, which seem to do a good job of mirroring actual rates, with the regular season rate in each year. That way, we can see if the composition of the playoffs is naturally more strikeout-prone:

Postseason vs. Regular Season Strikeout Rate

Year Expected K% Reg Season K% Gap
2002 17.8% 17.0% 0.9%
2003 18.9% 16.5% 2.3%
2004 18.3% 17.0% 1.3%
2005 17.5% 16.6% 1.0%
2006 16.6% 17.0% -0.3%
2007 18.8% 17.2% 1.6%
2008 20.1% 17.6% 2.4%
2009 19.2% 18.1% 1.1%
2010 20.8% 18.6% 2.2%
2011 18.4% 18.7% -0.4%
2012 20.4% 19.9% 0.5%
2013 21.7% 20.0% 1.8%
2014 20.9% 20.5% 0.5%
2015 21.4% 20.5% 0.9%
2016 25.5% 21.2% 4.3%
2017 25.5% 21.8% 3.8%
2018 24.8% 22.4% 2.4%
2019 25.0% 23.1% 2.0%
2020 25.4% 23.5% 1.9%
2021 25.1% 23.3% 1.8%
2022 25.2% 22.5% 2.7%

Since 2016, the playoffs have been a far more strikeout-friendly environment than the regular season every year. It’s no coincidence that average start length declined precipitously in 2016 and hasn’t recovered since; every year has had a lower IP/GS mark than every year before 2016. Relievers are covering more innings, and simultaneously, expected strikeout rates have boomed.

This year has been no exception. The most-used relievers in the postseason are striking their opponents out at a ridiculous clip. José Alvarado is tied for the most batters faced this postseason. He struck out 37.9% of his opponents this year. Seranthony Domínguez is right behind him, and struck out 29.5% of his opponents in the regular season. The Astros’ two most-used relievers are Rafael Montero (27% strikeout rate in the regular season) and Bryan Abreu (35.5%). Teams are using high-strikeout relievers as often as they can, because those are the best relievers, and every inning is of huge import. Relievers have struck out a whopping 29.7% of the batters they’ve faced this postseason. It’s not just Domínguez’s gaudy 56.3% rate, either: exclude him, and relievers are still striking out 29% of opponents. The pitching talent level is just phenomenal.

That’s my guess for the culprit. As for this year’s higher-than-expected strikeout rate, I’m not entirely sure, but I’m inclined to ascribe it to random variation. There are great pitchers in the playoffs every year, and great hitters too. They have to play each other in real life, not on paper, and how they’re feeling on a given day could be the difference between a strikeout and a walk, or between a batted ball and a whiff.

So don’t despair, strikeout haters: the 2022 playoffs aren’t some new paradigm. But also, do despair: the paradigm shift happened in 2016, and it doesn’t look like we’re going back. The playoffs are now the domain of high-octane relievers and more strikeouts than the regular season. It’s not just nerves, or weather, or extra velocity. The way the game is played in October simply leads to more strikeouts because of which players teams use.

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