March 17, 2017
Roberto Osuna's Complicated Relationships
Earlier this week BP Toronto ran an excellent article by Kyle Matte about Roberto Osuna’s evolving array of breaking stuff. Specifically, Matte wrote about Osuna’s development of a cutter in 2016, and the way (as he observed, providing considerable evidence) it somewhat cannibalized his slider. Whenever a pitcher adds a new pitch to his arsenal there’s reason to hope that it will add a new dimension to his game, but there’s also cause to worry that it might eat into the effectiveness of one or more of his other pitches.
Last week, I wrote about Dan Straily’s effort to flesh out his two-seam fastball this winter and about his expressed concern that doing so would compromise his changeup or slider. As I did with Straily’s sinker, though, I thought I'd dig into Osuna’s tunneling numbers to see whether the cutter offered a benefit that might make the tradeoffs worthwhile. What I found was pretty interesting, so I thought I would briefly share it here.
See, I think Osuna’s cutter actually has the potential to be a devastating weapon. He might just need to deploy it more strategically. First, some basic data. Osuna did see a change in the sequence interaction of his fastball and slider, from 2015 to 2016, and it’s safe to say that the introduction of the cutter drove that change.
Roberto Osuna, Fastball-Slider (and Fastball-Cutter), 2015-16
You can see some of what Matte was seeing (from the less granular perspective of PITCHf/x pitch characteristics) in this table. Two things seem to have happened:
In a vacuum, however, those cutter numbers are dazzling. Of the 134 pitchers who threw a [four-seamer, cutter] sequence at least 10 times last year, Osuna’s combination had the smallest tunnel differential, by far. The pitch pairing had an above-average post-tunnel break differential too, so no lack of movement minimized the value of the tunnel differential. However (and here’s where things get interesting), Osuna’s plate differential for that pitch sequence was the smallest of the aforementioned 134, by another healthy margin.
What that’s all telling us is that Osuna simply doesn’t have the optimal plan for his cutter yet. He’s throwing the pitch to the same part of the zone as the fastballs that precede it, and while that might be optimal for starters (who occasionally need to trade whiffs for weak contact) it doesn’t suit Osuna’s role or his repertoire. If he can’t figure out how to throw the pitch out of the same arm slot as the fastball without throwing it to the same location, then Matte was right: he should scrap it. If, on the other hand, he can get sufficient feel for the pitch to allow him to throw it to both sides of the plate, he’ll have a legitimate and occasionally dominant fourth pitch.