Luis Severino is in the Yankees rotation to stay

Two nights ago, both YES Network broadcasters, Michael Kay and Ken Singleton, made an interesting claim—that Luis Severino is, as of now, the best pitcher on this Yankees team. It’s not that far-fetched of a claim, either: through ten starts a piece (other than Jordan Montgomery’s nine), Severino has the lowest ERA (2.93) and FIP (3.05), second-lowest DRA- (51), and the highest strikeout rate (10.13 K/9) on the team. Unless you’re going to continue arguing that Michael Pineda’s underlying peripherals make him better, the best starter has been Severino.

What a journey it’s been for such a young pitcher. Let’s take a trip back in the time machine to 2015, when young Severino was merely a twinkle in our eyes. Back in those days, he was “just” a very young flamethrower with two pitches and a small-ish body for someone billed as a starter. In this NJ.com article from that year, here’s what Chris Crawford and Keith Law had to say:

This isn’t to denigrate either writer—they’re both two of the most reputable scouts in the public sphere. Evaluating baseball players is incredibly hard, though, and we honestly have no clue what a ballplayer like Severino is going to look like one, two, or five years in the future, largely because the profile is a really difficult one; and, justifiably, one that leads to more injuries on average, and more shifts to relief pitching on average.

Yet here we are two years later, and Severino remains in the rotation. I think he’s going to be there for the foreseeable future. Here are a few things, from even before the season, that bodes well for him.

Most importantly, pitching coach Larry Rothschild told him that he needed to keep his pitches down in the zone and located properly, and to focus on throwing his change effectively.

If you compare where he threw pitches in 2016...

...to where he has thrown pitches this year...

...then you’ll see that, in general, his pitches are closer to the lower third of the zone, which helps a ton when you see his opposing slugging percentage by location:

Another thing is really interesting: he has significantly boosted his usage of the slider, easily his best “out pitch”:

The outcomes, to no one’s surprise, have been better than in the past. By whiff percentage, all three pitches have improved, and the slider by a significant amount, without even having to throw it harder:

This is mostly because not only is he throwing down in the zone more often, but he’s throwing the slider with more downward action, as opposed to a traditional east-west slider:

This doesn’t mean these improvements are going to stick, or that his current performance will keep up, because that probably doesn’t happen. If I’m pumping the brakes a bit, which is wise to do, then one would say Severino is a true talent ~110 ERA+ pitcher in the future.

That’s not bad at all! In fact, he has a 103 ERA+ already in his career. I think it’s absolutely possible he breaks out and becomes something like a 120 ERA+ pitcher—that’d be huge. Even if he’s “only” 10% better than league average moving forward, you take that.

There are a few things that don’t work in his favor, though. His hard-hit rate is about exactly the same as 2016, in a way showing that last year he was under-performing a bit and vice-versa now. That combined with a home run rate of about one per nine innings means there are just going to be some bad starts—a three run home run here or there can wreck a game or an ERA. He also still just has three pitches with a clear strategy, so expect the league to adjust accordingly.

Despite some of his weaknesses and possible caveats in his good start, I think he’s proven he’s here to stay. Once you’ve crossed the threshold of nearly 200 major league innings of league-average ball, with the quality of his stuff, it really just comes down to game-to-game consistency, something we can’t really quantify or project. With question marks abound on this staff, Severino could very well be the young rotation stalwart the Yankees have needed.