March 17, 2017

Rubbing Mud

Roberto Osuna's Complicated Relationships

by Matthew Trueblood

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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:

1. Osuna took some percentage of the situations in which he would normally follow up his fastball with his slider, and instead threw the cutter. He used the cutter more often against lefties than against righties. He seems to have selected situations in which he had just thrown a fastball somewhere near the first-base side of home plate, and needed to throw a pitch that played off that one and ended up in a different spot, but didn’t feel he could safely use the bigger-breaking slider to do it.
2. In switching from one breaking ball to two (or one-and-a-half), Osuna slightly altered the arm slot out of which he threw the slider. That allowed him to spin the slider slightly differently, with a spin axis geared more toward sink and less toward sweep, and left the cutter for the situations in which he needed lateral movement most. It also made the slider easier to differentiate from the fastball, out of the hand.

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.

Specifically, I'd counsel Osuna to invert his mental concept of the pitch. He’s been throwing it more to lefties than to righties, and when he throws it to righties he’s been throwing it to the outer part of the plate, basically where he would put a slider. To best avail himself of the unique characteristics of his cutter, though, he should instead use the offering more against righties, forming a fastball-cutter-slider repertoire against them and leaving the fastball-changeup-slider arsenal against lefties.

To maximize the value of the cutter’s small tunnel differential and high velocity, he should throw it at those righties’ front hips and let the pitch run over the inside corner. If he picks his spots and can command the pitch to that location, he can get a lot of broken bats and called strikes doing that. If he can’t command the pitch to that spot, again, it almost isn’t worth keeping.

As long as he remains a closer, Osuna really doesn’t need such a complex arsenal and the tradeoffs he’s made just to come this close might not be worth the potential reward. Perhaps, though, this is a small shred of evidence that Osuna could one day transition back to a starting role. It’s easy to forget (but important not to) that the Jays radically rushed him to the majors two seasons ago, and that he’s still only 22 years old.

Matthew Trueblood is an author of Baseball Prospectus. Follow @MATrueblood
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