Why Jacob deGrom is for Real

When a rookie starting pitcher posts a 2.69 ERA and earns Rookie of the Year honors, despite owning an unexciting 3.62 career ERA in the minor leagues, the natural knee-jerk reaction is to raise both eyebrows. When that pitcher also struck out 25.5% of the batters he faced in the Majors, after posted an underwhelming 19.5% strikeout rate in the minors, you would raise a third eyebrow if you had one. But despite his mediocre minor league track record that fails to foreshadow the type of success he enjoyed during his Mets debut, Jacob deGrom is for real. Here’s why:

He Possesses a Full Pitch Arsenal

Technically, he throws five pitches if you count both fastballs. So he throws both a four-seam and two-seam fastball, which average above 93 mph, representing good velocity. He complements the fastball with his favorite secondary pitch, the slider. He threw that pitch 16.5% of the time, and it averaged 87.0 mph. Along with the fastball and slider, he offered two off-speed looks with both a curve and changeup. The curve was thrown nearly 10% of the time, coming in just under 80.0 mph, while he threw the change about 12% of the time at nearly 84.0 mph.

Five pitches, ranging from 79.4 mph to 93.5 mph on average. If you take his minimum and maximum velocities into account, he attacked hitters with pitches as slow as 74.9 mph and as fast as 97.4 mph. That’s quite the spread and makes it difficult for batters to guess what’s coming next.

His Full Arsenal is Damn Good

A full arsenal of pitches to work with is great and all, but if they all stink, it’s of little benefit. Well, deGrom’s repertoire is far from stinky. Check out his SwStk% by pitch compared to the benchmark:

That’s four of five pitches that induce swings and misses above the league average, some significantly so. And the slider still generates swinging strikes more than 10% of the time, so it’s certainly not a poor offering. As Eno observed in late August, deGrom started throwing his slider harder, basically after his first five starts. However, his pre- and post-velocity change whiff rates were nearly identical. So if the increased velocity boosted his performance, it wasn’t from more swings and misses on the pitch.

The huge advantage of having such a deep arsenal of above average pitches is that it gives him significant downside protection. Maybe the four-seamer won’t generate a nearly 11% SwStk% again. In fact, I would bet that it doesn’t myself. Fine, he still has three other strong pitches to lean on more heavily. He threw his change just 12% of the time and yet it was one of the best in baseball. And that curve was fantastic too, yet it was thrown just about 10% of the time. There is a ton of room to increase the usage of those pitches in order to sustain a similar overall rate of whiffs. This, of course, assumes that increased usage won’t reduce the effectiveness of the pitch, which is always possible.

He’s Got Ground Ball Rate Upside

deGrom posted a ground ball rate of 45.4%, which is just above the league average. But his ground ball rate surged to nearly 58% at Triple-A before being called up and he posted marks in the high-40% range during previous minor league stints. While he threw just 38.1 innings in Triple-A this year, representing a fairly small sample size, batted ball distribution does stabilize rather quickly. His two-seamer, changeup and curve ball all induced ground balls over 50% of the time. When you remember that the latter two pitches also generated high SwStk% marks, you realize they are potentially plus-plus. And if he does increase their usage next season, his ground ball rate would rise.

He Flashes Excellent Control

deGrom threw 66.1% of his pitches for strikes, well above the league average this year of 64.3%. That mark was good for 30th in baseball among starters. He also had no trouble throwing first pitch strikes, as his F-Strike% attests. His 62.8% mark ranked 35th among starters. And although I like to stay away from results and focus on the underlying skills, his highest walk rate in the minors was just 7.7%.

There are obvious reasons to doubt deGrom’s surprisingly dominant rookie performance. But with his assortment of pitches and strong control, significant regression appears to be highly unlikely. I’m taking the under on Steamer’s 3.92 ERA projection and the over on its 21.0% K% projection.