Gerrit Cole Has Made a Tweak

Despite playing for the Yankees and having the largest contract ever handed out to a pitcher, I think Gerrit Cole’s start to the 2021 season is going under the radar. Now, I have no empirical evidence that this is the case, but go with me here. I think two things are at play. First, Jacob deGrom is striking out every batter he faces (do not fact check me on that) and plays in the same city. Second, the Yankees’ struggles have been the talk of baseball in the early going, with much of the focus centered on the lineup and rightfully so. The team’s performance thus far has been extremely underwhelming, though they are 9-4 since their 5-10 start.

None of the blame for the Yankees tepid beginning can be put on Cole, however. He is off to a fantastic start. Through his first six starts, he has struck out 44.3% of the batters he has faced and walked only 2.1%. That strikeout rate is third in the majors behind deGrom and Corbin Burnes; the walk rate sits fourth in the league behind Burnes, Zach Eflin, and Walker Buehler. Put those two figures together and Cole has a K-BB% of 42.1%, only a few percentage points behind Burnes and deGrom and a shade under 10 percentage points above Joe Musgrove. The difference between Cole and Musgrove is about the same as the difference between Musgrove and Clayton Kershaw who is 19th on the leaderboard. Cole’s 2.4 WAR is tops in the league, though he has made one more start than both deGrom and Burnes, though I will note that he has only thrown two and two thirds more innings than deGrom so on a rate basis he has actually been more effective in accumulating WAR. Most of the difference has to do with a .315 BABIP allowed compared to deGrom’s .241 and a strand rate that is 8.3 percentage points lower.

So, Cole has been great. But this is not a breakout. Cole has been one of the best handful of pitchers in the sport since he first donned an Astros uniform in 2018. In the three preceding seasons, he posted a 36.6% strikeout rate and 6.8% walk rate over 485.2 innings, good for 6.05 WAR per 200 innings pitched. What is notable is that early on, he is pitching as well as ever. Better even. Since 2018, Cole only has one six start stretch where he struck out at least 44.3% of opposing hitters (44.6% from the end of July to end of August in 2018) and he has never posted a six start stretch walking so few batters (on a rate basis). At this point baseball fans are accustomed to Cole’s dominance over the opposition, but the degree to which he is doing so is unprecedented.

Cole’s pitch mix is largely unchanged, save for one notable exception. He has relied more heavily on his changeup than in any other season in his career:

Unsurprisingly the offering is saved for opposite-handed batters. The changeup is still his least-used pitch against right-handed hitters but when facing a platoon disadvantage, it is now the pitch he has turned to the second most-often, narrowly edging out his curveball (62 changeups versus 61 curveballs). He is using the changeup more against righties but the change is even starker against lefties:

I would say the change is for the best. After posting relatively neutral platoon splits in both seasons in Houston, Cole struggled (by his standards) against left-handed hitters in 2020. With the caveat that it is still very early in the season and outlier results are bound to regress, the pitch mix alteration has been effective: