How much better is the pitching in the postseason?

There were 831 human beings in the world who could call themselves an MLB pitcher in 2019. These are the truly elite of our species at this one absurd, specific skill: throwing a baseball in an area where a batter can hit it, while still somehow preventing him from doing so. Then, for the playoffs we removed all but 105 of those pitchers, including nearly all of the weakest ones. Being able to pitch in the postseason truly means being the best of the best.

If that is true, we should see some difference in pitch quality between the regular season and the playoffs. The average velocity and movement for each pitch type should be better because the people throwing these pitches are better. We’ll take a look at some of these pitch type averages to see if that holds true.

Measuring Pitches

First, a great big caveat: the baseball itself is different. Baseball Prospectus’ Rob Arthur detailed early in the offseason that the ball was dejuiced. Yesterday, he proved that as October progressed, the ball became wildly inconsistent. This definitely has an impact on how far a batted ball travels, but it should also affect pitch movement. Arthur concluded in yet another study that it does, but only an inconsequential amount. As such, we’ll press on with our comparison.

To compare regular season pitch type averages to their October counterparts, we’ll use Pitch Info data, available at Brooks Baseball. We can find the velocity and movement for each pitch thrown by every pitcher. By weighting them for number of pitches thrown, we can find league averages for the postseason. Fortunately, league averages for the regular season are readily available on the FanGraphs leaderboards, (which saves a ton of work!).

We’ll analyze pitches in three categories: velocity, vertical movement, and absolute value of horizontal movement. Using absolute value for horizontal is important because of the way Pitch Info describes pitches for lefties vs. righties. Pitches moving away from a right-handed batter are considered positive movement, whereas pitches moving towards a right-handed batter are considered negative. This doesn’t describe the quality of the pitches, just where they fall on a coordinate plane.

For example, Adam Ottavino of the Yankees and Ryan Yarbrough of the Rays both have elite movement on their sliders. The right-handed Ottavino was credited with an average horizontal movement of 11.2 inches in the postseason. Yarbough, a left-hander, had his slider's horizontal movement measured at -11.0 inches. That “negative” might imply that it’s incredibly poor movement, but in reality it’s just going the opposite direction as Ottavino’s.

Here’s an Ottavino slider:

Here’s one from Yarbrough (yes, it’s more of a slurve, but Pitch Info classifies it as a slider):

Clearly, they both have a ton of horizontal movement. Rather than cancelling each other out when we calculate league average, they should both be near the top of the data set. As such, we’ll look at absolute value for horizontal movement.

Using postseason pitch data from the Wild Card games through World Series Game Two, we should now be able to make some comparisons. Let’s break this up into three tables for easier digestion (all velocity is mph, all movement measured in inches).

Hard Stuff

The most common pitch in baseball is the four-seam fastball. Only eight of the 105 postseason pitchers didn’t throw one. 811 out of 831 regular season pitchers featured a four-seamer. In many ways, it’s the best measuring stick for a pitcher’s overall stuff.

A 1.3 mph jump on average from the regular season to the playoffs is pretty significant, as is a 0.8 inches of increase in vertical movement. This definitely seems to support the hypothesis of higher quality pitches in the postseason. The reason why is pretty clear: 20.5 percent of all four-seamers in October so far have been thrown by one of Gerrit Cole, Justin Verlander, or Max Scherzer!

Cutters and sinkers are really just variations on the fastball (Pitch Info doesn’t have a category for twoseam fastballs). These both have mild increases in velocity of less than a half mph and movement of less than half an inch vertically and horizontally. They’re a little better, but not enough to make much difference, and certainly not as much as the four-seamer.

Breaking Stuff

The curveball is more than a full mph harder in the playoffs— despite the best efforts of Zack Greinke and Rich Hill! There’s a wide range though, spanning from Liam Hendricks’ 86.4 mph to Patrick Corbin’s 67.9.

When it comes to curveballs, negative vertical movement is a good thing. The further negative, the sharper the drop. In the postseason, they’re breaking more than a half inch lower than the regular season. That could be the difference between a line drive and ground ball off the bat (obviously batters adjust their swing plane to an extent, but just roll with it). There’s also about an inch and a half more horizontal movement, making it even tougher to square up October curves.

Sliders are usually intended to break more horizontally than curves. The 0.6 inch horizontal movement increase in the playoffs means that these are a little more crisp as well. The velocity and vertical movement really don’t differ that much from the regular season though.

Offspeed Stuff

Some of the game’s best changeups have been featured in the postseason. 42.0 percent of all changeups have come from Stephen Strasburg, Max Scherzer, Tommy Kahnle, Aníbal Sánchez, and Zack Greinke. Naturally, they’re more than a full mph harder with an inch more horizontal movement.

Splitters are a different animal— an endangered one, in fact. Twenty years ago, the pitch was in vogue. It was probably responsible for at least 2,000 of Roger Clemens’ 4,672 strikeouts. In 2019, only 67 pitchers threw one in the regular season. Just four of them— Masahiro Tanaka, Oliver Drake, Jake Odorizzi, and Aníbal Sánchez— threw a splitter in the playoffs. That’s probably not enough for us to make any real conclusions about the pitch, other than that it has fallen out of style.

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All in all, there’s a definite increase in velocity and movement across the board in the playoffs. Sinkers, cutters, and sliders don’t vary too much, but four-seamers, changeups, and curveballs have gotten a lot better in October. The main reason is that better pitchers take the mound more often, and most of the mediocre ones don’t get to participate at all. It’s a good thing the quality of the hitters increases, too. Otherwise we’d have a major run scoring shortage.

Daniel R. Epstein is an elementary special education teacher and president of the Somerset County Education Association. Tweets @depstein1983.