Are Pitchers Hunting Hitters’ Weaknesses, or Avoiding Their Strengths?

One advantage of living in an age where the wealth of human knowledge is at one’s fingertips is that no curiosity need go unsatisfied. I was just sitting around wondering idly about the relationship between how hitters get pitched and how well they do against certain types of pitches. So I ran a couple of Baseball Savant searches and played around in Excel over lunch and ended up with something that would surely have made Henry Chadwick soil his trousers.

Which probably overstates the impact of these findings, such as they are. One of my major takeaways is that Aaron Judge is a preposterously good hitter, which I feel like we all knew going in. Still, it’s a fun journey to go on, so let’s take it together.

Heading into Thursday’s games, 281 different batters had seen 500 or more pitches this season. I separated those pitches into three different categories: fastballs, off-speed, and breaking balls, and took each hitter’s wOBA against each of those pitch types.

Now, if I were working in a front office trying to get an edge on an opponent, I’d get more granular, because pitch classification is one of those things that doesn’t always lend itself to neat categorization. Not only are sliders different from curveballs, but not all sliders are alike. And some sliders, in fact, are more like cutters, which aren’t breaking balls at all. Then there’s sequencing, and most important of all, location. (Pitching is like the real estate market in two respects: First, location is of paramount importance. Second, cranky old people refuse to understand how different things are now than they were in the 1980s.)

Anyway, we’re not covering any of that today. This is as high-level a survey as you could ask for: How does each hitter fare against each class of pitch, and is the proportion of pitches he sees commensurate with those results?

For each pitch group, I compared each hitter’s wOBA against that group, as well as the percentage of total pitches seen from that group, against league average. Hitters in the top left quadrant hit fastballs very well but don’t see a lot of them; hitters in the bottom right see lots of fastballs but don’t hit them very well:

And while this chart looks fairly random — fastballs are a fundamental pitch; you’re never going to avoid throwing them completely — you can see a clear slope on the fit line. I highlighted five outliers in different colors to illustrate some of the outliers:

You can see the whole gamut here. Schuemann can’t hit the fastball, so he sees a ton of them, while Larnach kills fastballs and sees fewer of them than any other hitter in the league. Then there are Trout, Soto, and Kwan, who live at varying stops on the “Jeez, I guess we’ve got to throw them something” railway.

And there are different approaches to different hitters. Soto has the best fastball wOBA in the league, so pitchers will try their luck with anything else. In the decade-long search for holes in his swing — a search as arduous and costly as an expedition to find the Northwest Passage — elevated fastballs were the closest anyone ever got to a consistent weakness. So Trout, despite being an above-average hitter against fastballs, and faring better against them than he has against off-speed stuff this year, is still seeing one of the highest fastball rates in the league.

Which brings up another fun artifact of this search: The guys who just hit everything. Out of 281 hitters in the sample, only six have a top-50 wOBA against all three pitch groups:

That’s four of the consensus best hitters in baseball, plus two of the biggest first-half surprises this year. Good for Fry and Profar.

Let’s see how our fastball outliers got pitched in terms of off-speed stuff:

If you’re having a hard time seeing Trout and Kwan’s dots on this graph, I don’t blame you. Both hitters drifted back toward average here, and are seeing an appropriate percentage of off-speed pitches:

But now it should be even clearer why Schuemann sees so many fastballs and Larnach sees so few. Larnach is one of the 25 best fastball hitters in the league and one of the 15 worst off-speed hitters, so he sees literally the lowest percentage of fastballs and literally the highest percentage of off-speed stuff. Schuemann is the reverse.

Of the top 10 hitters in off-speed OPS, six — Rob Refsnyder, Travis d’Arnaud, Rafael Devers, Brenton Doyle, Ezequiel Tovar, and Willy Adames — are 200th or lower in off-speed pitch percentage. Once pitchers figure out where you’re strong, they’ll try to take that strength away. What about breaking balls?

Finally, a pitch group where Soto is merely above-average:

And finally, our answer to the question of why Kwan and Trout keep seeing so many fastballs: Because they’re just as good against breaking pitches as they are against heat.

Schuemann and Larnach are two of 12 hitters in the league who have wOBAs in the top 75 in two pitch groups but are bottom 75 in the third. Of those 12 hitters, only Pete Alonso (who has a wOBA of .214 on breaking balls, 241st out of the 281 hitters in the sample) is seeing a below-average serving of his weakest pitch.

So are pitchers generally attacking hitters where they’re weakest? Not really:

The top right-hand corner of this graph is pretty heavily populated because a lot of hitters stink at hitting two different groups of pitches. Javier Báez, for instance, is 276th in wOBA on fastballs, 233rd on off-speed pitches, and 273rd on breaking pitches. So while he’s technically bottom 10 in the league in seeing his weakest pitch group (relatively to the league), pitchers can basically throw him anything they want. He’s like the opposite of Judge.

Let’s flip that table on its head, though. How many hitters are getting an abnormally small helping of their strongest pitch group?

The top-left corner of this graph (high wOBA, low Pitch%) is much more heavily populated, even with the caveat that there are some guys, like Judge, whose strengths are so vast they’re impossible to pitch around. This season, 24 different hitters are in the top 10 in wOBA for at least one pitch group; 16 of those hitters are 200th or lower in Pitch% for that group. Another six are 100th or lower.

The only two exceptions are Brent Rooker (seventh in wOBA, 28th in Pitch% on breaking balls) and Kyle Tucker (10th in wOBA on fastballs, 60th in Pitch%). And Tucker is no lower than 41st in wOBA on any of the three pitch types — he’s almost in the Judge Zone. Rooker, at least, is 202nd in the league in wOBA on off-speed pitches.

Throw Brent Rooker more change-ups and splitters, I guess, is the moral of this story.