The Major League Baseball season is a long and grueling trial for players, and that’s especially true for young pitchers. They are often throwing more innings than they have ever thrown in their lives and that can lead to a dip in production. Ian York takes a look at New York Mets starter Jacob deGrom to see if he is showing any signs of slowing down.
Jacob deGrom is a fantastic young pitcher. He has followed up last year’s Rookie of the Year campaign with a 2015 season that almost any pitcher in baseball would kill for: an ERA of 2.64, FIP of 2.84, WHIP of 0.99 and ERA+ of 142.
His last few games, though, have been much less exciting. Although he has had a few solid outings in late August and September, he has mixed in some true stinkers (Aug 24 against the Phillies: eight hits, six ER in 2 ⅔ innings; September 15, against Miami: ten hits, six ER in five innings).
The simple explanation is that he is becoming worn out, since before his most recent start he had already set a new high for innings pitched at 181 (2808 pitches thrown). The Mets, very reasonably, skipped a start for him, and the extra rest seemed to help in his latest start (six innings pitched, five hits, one run).
Just “tired”, though, is not actually an explanation for a pitcher’s struggles; the tiredness has to spill over into the way he pitches somehow. It could mean, for example, that fastball velocity or curveball movement is lost, or that he is missing his locations. We can look at deGrom’s pitches and see if there are any red flags.
deGrom throws a four-seam fastball in the mid-90s, an excellent changeup, and a slider, curve, and sinker. We can look at his pitch mix, game by game (using Brooks Baseball’s data to categorize pitches; omitting his most recent game on September 27, when he pitched with extra rest), and compare that to his outcomes:
There is no really obvious trend, but we can see that in his most successful period (about May through July) he threw fewer sinkers (“SI”, according to Brooks Baseball; PITCHf/x calls these “two-seam fastballs”, or “FT”), and in April and September, when his outcomes were worse, he threw relatively more of them (replacing the slider as his major secondary pitch).
FanGraphs shows pitch value, but doesn’t break out two- and four-seam fastballs, and doesn’t break them out by game. We can look at a similar thing by calculating total bases per 100 pitches on a monthly basis:
(Since these values come from PITCHf/x, the sinker is called “FT” here.) Several things show up in this. First, except for his curve (his least-used pitch) all of his pitches follow a U-shaped curve, with their lowest (best) values in May through July. But the sinker/two-seam has deteriorated far more than any other pitch; in September, it’s been simply terrible.
None of his pitches have really lost velocity or movement:
In particular, his sinker/two-seam has maintained velocity and movement throughout the season, so that doesn’t explain why it was so ineffective.
If the raw quality of the pitch is unchanged, then the next thing to look at is pitch location. We can look at the distribution of deGrom’s two-seam by month, as thrown to right- and left-handed battters. (These charts are from the umpire’s viewpoint, so the batters would stand in the center of the charts. The grey polygon is the de facto strike zone as it has been called this year.)
Here, there is a dramatic change in the last couple of months. Early in the year, deGrom was throwing his sinker on the edge of the strike zone (outside the left-handed batters, inside to righties). In August, he seems to have lost his location to right-handed batters, with most of this two-seams in the center of the strike zone, though mainly in the lower third. In September, his two-seam is spread out over the entire strike zone to righties, and even to left-handed batters a significant number have moved over the center of the zone as well. deGrom seems to have shown his fatigue by losing his usually excellent location and grooving many of his sinkers in the heart of the strike zone.
Notably, in his most recent start (with extra rest) he only threw two sinkers out of 96 pitches; based on his previous patterns we would have expected 10-20 of them. He may have decided that this pitch simply isn’t working for him at this point of the year. He has enough quality pitches that he probably can reduce the sinker usage and still be an effective pitcher. If not, the Mets may have a shorter post-season than they hoped.