Hitters Shouldn’t Swing Against Jacob deGrom

Jacob deGrom is on another planet right now. You don’t need me to tell you this, but it’s fun to just marvel at his stats. Through 10 starts, deGrom has a 0.56 ERA, a 46% strikeout rate, and a 4% walk rate. He’s produced 3.7 WAR, which is nearly a half-win better than the next-best pitcher, Corbin Burnes, who has “merely” put up 3.3.

deGrom is quite possibly in the midst of one of the best pitching seasons in baseball history, particularly on a per-inning basis. Pedro Martinez’s 1999 campaign currently holds the single-season pitching WAR record at 11.6, and though deGrom almost certainly won’t hit that mark, he’d blow it away if he pitched the same number of innings at his current rate. Give deGrom Martinez’s 213.1 innings, and at this pace, he’d put up 12.3 WAR. Say what you will about injuries and starting pitching workloads in this era, but that’s just a primer on the level of dominance deGrom has reached so far in 2021.

So if you’re a hitter stepping in against deGrom, how in the world do you get a hit off this guy? Batters are slashing just .121/.152/.220 against him, good for a .163 wOBA allowed. That’s the best mark among the 294 pitchers with at least 100 batters faced this season, and deGrom has more than doubled that threshold (223 TBF). If you’re hitting against deGrom, you’re lucky if you just put the ball in play, let alone get on base.

Is there an alternative strategy that works here? deGrom is raking up all of these strikeouts — without allowing virtually any walks — while boasting the seventh-lowest Zone% in baseball. Hitters are flailing against pitches that aren’t even strikes anyway: 60.5% of the time, deGrom is throwing the hitter a ball. If you’re in a two-strike count, he’ll throw you a ball 64.5% of the time, putting him in the 91st percentile in O-Zone%.

As you’ll notice, deGrom isn’t at the exact top of the charts in O-Zone%, even with two strikes. But deGrom is unique (when is he not?) because he is by far the most dominant pitcher after reaching a two-strike count. Of the 228 pitchers who have reached two-strike counts in 100 different plate appearances this season, deGrom’s .151 wOBA allowed is more than 30 (!) points lower than the next-best mark, posted by Tejay Antone (.181). Take a look at this scatterplot comparing two-strike O-Zone% and wOBA allowed after getting to two strikes:

The only other pitchers even in deGrom’s ballpark are Giovanny Gallegos and Mark Melancon, both relief pitchers who only have faced 20 more hitters combined than deGrom alone (243 for Gallegos plus Melancon vs. 223 for deGrom). The only other pitchers with 200 batters faced who are even relatively close to deGrom in either O-Zone% or wOBA allowed are Kyle Gibson (66.2% O-Zone%, .248 wOBA) and Brandon Woodruff (52.0% O-Zone%, .183 wOBA).

Because of deGrom’s near-the-top O-Zone% in two-strike counts as well as his best-in-the-majors wOBA allowed after reaching two strikes, should hitters just… never swing? This isn’t the first time this thought exercise has been entertained; this March, Maxwell Bay wrote an interesting article asking the same question about Shane Bieber on the FanGraphs community page. One big difference between 2020 Bieber and 2021 deGrom, though, is their respective walk rates: Bieber walked 7.1% of hitters last season, while deGrom has walked just 3.6% this year. But it’s not solely about the results: Bieber’s overall Zone% last year was 34.0%, while deGrom’s this season is 39.5%. Considering the difference in the two pitchers’ walk rates, perhaps hitters aren’t taking enough against deGrom in actuality.

Ultimately, though, does the same logic apply here? Should hitters just go up to the plate against deGrom with the take sign on in every situation? My friend Jeremy Frank approached me with this question and some data to support the answer. Looking specifically at the two-strike counts, here’s the probability that each hitter will walk — and the associated wOBAs — after getting to each count versus deGrom:

In each row we have the data for each count, including the Zone%, the probability of working a walk, the expected wOBA doing nothing but taking, deGrom’s wOBA allowed after reaching said count, the wOBA difference, and how many more runs each hitter would be expected to produce over 600 plate appearances by only taking versus actually hitting. The probability of working a walk is a simple calculation, using conditional probability with deGrom’s Zone% by count to get the hitter to a walk. If you’re at 0-2, for example, you’d need deGrom to throw you a ball four times in a row, on each of the 0-2, 1-2, 2-2, and 3-2 counts. That walk probability accounts for all of his observed Zone% figures.

This look at deGrom’s tendencies assumes that everything is independent, which obviously isn’t a fair assumption given that he’s likely to change his tendencies based on each individual plate appearance. But the data clearly show that there might be some method to this madness, similar to how hitters would be much better off not swinging at any of Bieber’s pitches, as Bay showed. In fact, looking across all plate appearances, in order to produce better results against deGrom than hitters have so far, you would “only” need to walk in more than 23.6% of plate appearances. If you think it’s more likely deGrom will throw you four balls than three strikes more than 23.6% of the time, it is better to always take.

We can do a similar exercise for all major league pitchers, focusing particularly on those two-strike counts. How much does deGrom separate himself from the pack? Are there other pitchers for whom taking every pitch is a viable strategy? Similar to deGrom, I went count-by-count. Here are the five best pitchers to take against in each two-strike count. There are definitely some tiny samples here, but it’s still interesting to see the results so far.

First, 0-2:

Next, 1-2:

Third, 2-2:

And, finally, 3-2:

Then, we can take an average of each of the wOBA differences by count and find the best pitchers to always take against in two-strike counts. Here are the best pitchers to always take against:

This is a pretty fascinating list. It’s a combination of guys with elite stuff who survive on getting hitters to chase frequently as well as those who walk almost everyone. That makes sense, though. You’re better off waiting out elite pitchers because if you make contact, you’re likely going to get out anyway. And you’re also better off waiting out guys who can’t find the zone because waiting for a walk is better than getting yourself out.

If you set the minimum number of two-strike pitches to 200 to filter out some of those relievers, we find that it’s better to always take versus only these seven pitchers:

There we go: deGrom is one of the only starting pitchers against whom this “works,” if we can even say that. We know that this will never work in practice: If each hitter only took against deGrom, they should expect to see 102 down the middle of the plate soon enough, I’d bet. But if you’re going to do this every once in a while — in an important spot, perhaps — the data agrees with you. If you’re facing Jacob deGrom, it’s best for a major league hitter to do nothing but marvel at his offerings… and hope that he throws four balls before he throws three strikes.