Baseball is crazy because of how much it can change even day to day. The best team in baseball could lose to the worst team in baseball on one day, and then show their true colors on the very next day. It was the same team all along, but each day another facet can emerge. As time is lengthened those day-to-day inconsistencies seem to erode, but year to year trends can appear to be just as shaky. Teams that were juggernauts one year could fall apart the next with largely the same roster, and teams that seemed altogether mediocre could have a breakout the next year. That’s the case with players as well.
The player that fits this mold very well on the Yankees is Luis Severino. Severino, a year ago, had quite a different portrayal in fandom and in the media. Just a year ago, Severino was actually a member of the bullpen, and doing quite well. After a rather disappointing 2016 as a starter, and a half-season demotion, he emerged later that year as a formidable long man out of the pen.
Luckily, the plan was for this not to be permanent. Joe Girardi even conceded at the time that “Sometimes I think when you move him into a bullpen role you can simplify things for him a little bit. They don't need as many pitches to be successful. We still think his changeup needs development, but we're fighting for a spot and we feel that's maybe his best role at this time.”
The concern, of course, is that this would be a Joba Chamberlain situation. He has one good role, in the bullpen, and the organization continually shuffles him between that and the rotation, never giving him a consistent rhythm to work with.
Flip the calendar a year forward, and I think we can see the Yankees made the right decision, informed by what Girardi said about the stint being used to simplify his mechanics in preparation for a rotation spot. Now, if you look at where he stands in the major league standings in fWAR and PWARP, you can see that this is no fluke. By fWAR, he’s fourth in baseball:
By PWARP, which is largely considered to be a better indicator of future success than FIP, tells a similar story:
The only other breakout there is Jimmy Nelson, but without him, this is essentially a list of pitchers you would want to start a franchise with, pitchers you would take in a fantasy draft to build your rotation around.
It just makes it remarkable that you flash forward a year from “we’re not sure if he leaves the bullpen” to “consensus top ten pitcher in baseball.” And after he out-dueled Chris Sale himself on Sunday, it’s pretty obvious that he can compete alongside any pitcher in baseball on a given day. He’s for real.
When Girardi mentioned simplifying things, release point is definitely one of them. When you compare 2016...
...you can see that what almost looks like a v-shaped formation of release points is now almost a single dot, meaning that all three of his pitches appear exactly the same out of the hand. Being in the bullpen can help that, as a consistent motion from the stretch simplifies the release point with fewer motions.
The real result, which you can’t totally see on the charts, is how many whiffs he’s generating. That’s really the best way to evaluate a pitcher, because it’s the best indicator of showing the number of times a hitter was truly fooled.
The high occurrence of whiffs is really due to... command. It’s not just pitching within the zone and throwing; Severino did that in 2016 and got hammered. It’s getting an O-Swing% higher by three percentage points, and a swinging strike rate higher by three percentage points. If you locate and command your pitches, we’ve seen how that slider dips out of the zone.
Severino is a star pitcher. He will likely go through his troubles, as all young pitchers do, and he’s going to have to keep evolving—adding another pitch to throw the second and third time through the order, always working on his command. If you consider how young he is, though, the fact he even made it this far is remarkable. The Yankees haven’t had a homegrown Yankees star starter in a very long time. It has been fun to see the Baby Bombers making waves, especially when you remember that Sevvy is a Bomber in his own right.