Jacob deGrom hit the majors last year forcefully. In only 140.1 innings, he gathered himself 3.5 fWAR, a rate of just about 5 fWAR/200 innings. I'd say that's ace status. He did it without a ridiculously low BABIP, only .297. He had a little bit of luck on his left-on-base rate, 77.4%, but many of the best pitchers have such rates because they're the best. Really, deGrom got where he did due to his high strikeout rate and low home run rate. Those are supposed to be things within his control.
Despite that success, the projections see a slight downfall, which makes sense. deGrom had never struck out opposing batters at such a high rate in the minors. However, the control and homer-limiting abilities were there in the minors, and deGrom's 2.69 ERA was not egregiously out of line with his peripherals (2.67 FIP, 3.03 xFIP). deGrom has a foundation for continued success, and it starts with his fastball. He throws a solid 93-94 from the right side, and he can locate the pitch well. Observe the zone profiles from Brooks Baseball against righties and lefties, respectively.
It is, perhaps, predictable. When he throws a hitter a fastball, it's most likely on the outside corner. However, this shows deGrom has the ability to hit each corner when desired.
Although deGrom's four-seam fastball location might be predictable, he stays relatively unpredictable. He doesn't show any strong tendencies based on the count.
While he focuses mostly on the fastball, he doesn't appear to eliminate completely any pitches from his repertoire in any count with the possible exceptions of a changeup as the first pitch against righties and throwing curves against lefties when the batter is ahead in the count.
Another element of unpredictability comes in the interplay of deGrom's fastball with his changeup. From Brooks Baseball, here is a description of deGrom's changeup:
His change is a prototypical pitch with few remarkable qualities.
Well that's not a glowing review, but it compares well against his right-handed compatriots. I looked to Baseball Savant to get some averages for right-handed pitchers, so these numbers differ a bit from Brooks Baseball's.
deGrom gets quite a few more whiffs than average, but he gets fewer ground balls than average. I think that's a decent tradeoff. Overall, his changeup seems to be pretty good. But, if there's nothing really special inherent in it, why does it get good results? It's the interplay.
One element of the fastball-changeup interplay is the velocity difference. deGrom's velocity difference between his four-seam fastball and changeup according to Baseball Savant's numbers: 9.7. It's 9.8 by Brooks' numbers. deGrom has the velocity difference covered.
Another element is the release point. If hitters can tell which pitch is coming based on where the release point is, then there won't be much deception. deGrom has the release point stuff covered. Here is a Tableau screenshot of deGrom's average release points for his four-seam fastball, sinker, and changeup.
All three of them are basically on top of each other. So, when deGrom is at that release point, the hitter can't tell if it will be a fastball or a changeup. deGrom has the deception part covered.
There's the movement part, which affects the location part. deGrom throws his changeup mostly to lefties, so here's his zone profile of changeups thrown to lefties.
He keeps it mostly low and away against lefties, as you would expect. His changeup dives quite a bit more than his four-seam fastball, so its overall location is lower than the four-seam fastball.
Overall, deGrom has the fastball-changeup interplay covered. He throws them from the same release point and can locate each pitch in the same place, but the velocity differential and vertical movement appear to play havoc with opposing hitters. I would imagine the deception plays a role in his changeup's markedly higher swing rate compared to other right-handed pitchers' changeups. deGrom's curve might be the better pitch in terms of making hitters miss when they actually swing, but his changeup has the highest whiff rate of his whole arsenal. The fastball-changeup interplay can make an unremarkable pitch on its own into something rather remarkable.
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