What Padres reliever Luke Gregerson is doing is unquestionably working. I tabbed him as the player most deserving of an All-Star bid on the team, and pick your stat, he’s been phenomenal.
His approach, of course, is pretty rare: the reliever uses his slider 61.1% of the time, working his fastball in 35.4% and changeup 3.6%.
Very few pitchers throw a breaking pitch as their primary offering, unless you call a cutter a breaking pitch.
Gregerson’s slider is fantastic, and it’s a huge part of why he’s been unbelievably good this year.
What’s interesting, though, looking at his Pitch Type Linear Weights, is that while the slider is 3.76 runs above average per 100 pitches this year, Gregerson’s heater (4.05) and changeup (4.52) are actually rating as even more effective this season.
Now, neither Gregerson’s 89-93 mph heater nor his infrequently-used changeup are the most impressive of pitches on their own, although they have a bit of cut and sink. Undoubtedly, a large portion of their success is due to hitters looking for the slider and not being able to adjust to the other two pitches.
Still, if they’re working, does Gregerson really need to lean this heavily on the slider?
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I wouldn’t ask this question if it was purely a question of performance; obviously, Gregerson’s slider-heavy approach is working fantastically for him.
But, when you’re talking about leaning this heavily on a breaking pitch, the issue of Gregerson blowing out his arm at some point looms.
A couple precedents are worth noting here. First, Gregerson spent some time on the DL with a strained right shoulder last year. The second is that A’s reliever Michael Wuertz, who is essentially the AL version of Gregerson, almost to a tee, got hurt this spring with elbow tendintis and hasn’t been right all season, missing a month and seeing a 2 mph drop in velocity. It took Wuertz half a decade in the majors to experience that, but it looks to be a serious issue for him.
Now, hey, if Gregerson were to start throwing more fastballs and then see his performance suffer, fine, go back to the current approach–the better performance outweighs the injury risk.
But if he’s capable of going to a 55% fastball/35% slider/10% changeup arrangement, or something around there, and still being a 2.00 ERA pitcher, Gregerson absolutely should. As a middle reliever in the NL, he’s going to get worked hard, so if his fastball and changeup are good enough for more frequent use, he should use them more frequently. Doing so would, of course, make the slider even more devastating, as hitters could no longer just sit on the pitch.
Another thing Gregerson could do is take a six-week stretch or so out of every year and use more of a fastball/changeup approach then. Hitters would still be surprised in such small samples, and by the time the scouting reports would be updated to reflect the change, Gregerson would go back to throwing the slider 2/3 of the time. That would be a neat way to save his arm a bit of stress every year with no performance issues.
They say not to mess with success, but Gregerson might benefit from laying off the slider more, at least for small stretches every year, in the long-term.