That's a pretty massive difference in spin rate and velocity, perhaps even moreso when you split it into "before" and "after." Eovaldi's new splitter really began to appear on June 26 against the Astros, and you can see that not only did he gain 4 mph and nearly 600 RPM, but also a great deal of confidence in the pitch -- simply in terms of how often he used it.
Splitter through June 25: 85.01 mph, 879 RPM, 12.7 percent usage
Splitter since June 26: 89.17 mph, 1,478 RPM, 21.3 percent usage
In 11 starts since, heading into Monday's matchup with Scott Feldman and the Astros, Eovaldi has a 3.29 ERA (2.95 FIP) and has limited opponents to a .608 OPS against. He's turned his season around from being the talented-yet-inconsistent flamethrower to one of the Yanks' most reliable starters, especially given the injury concerns around Michael Pineda.
Obviously, that velocity difference jumps off the screen. Eovaldi's been throwing everything harder, including his fastball, which is up to 97.82 mph, harder than any starting pitcher in baseball over the last two months. In a 4-3 win over the Twins on Wednesday, he touched 99 mph 29 times, more than anyone has done in a game this year. Nothing's seen an increase quite like that splitter, however, and it would be difficult to make a jump like that without adding more RPMs.
But while it would be tidy to say that going from low spin to high spin is a straight line to success, that's not always the truth. A traditional splitter, like the one Masahiro Tanaka throws, tends to dive "off the table" at the last second and is often used as a strikeout pitch. Higher spin for a splitter is often not ideal, because more spin creates more lift, and splitters aren't supposed to stay up.
Eovaldi's created himself something a little different than that. What his new grip has done, in addition to adding velocity, is change movement horizontally, not vertically. Through June 25, that splitter was moving 2.27 inches horizontally; since, it's jumped to 5.97, which is a pretty significant difference. And while the while the spin is higher for him, it's still not high. That is, of the 28 pitchers to throw 30 splitters since that same June 26 cutoff point, Eovaldi's 1,478 RPM is just 19th (Tanaka's, for reference, is 1,711 RPM). What's of interest here is whether a pitcher has the capability to considerably change his spin rate in-season, and in Eovaldi's case, he has.
Despite all the changes, Eovaldi's splitter isn't suddenly a knockout pitch like Chris Archer's slider or Felix Hernandez' changeup. The outcomes with the pitch aren't even all that different so far before and after the grip change. What's different is that now that he's shown it to be a viable offering, he can keep hitters from sitting on that fastball, which is down from 52 percent usage to 43 percent. And Eovaldi can use his slider less, which is down five percentage points. Batters have a lot more to think about, and it's a lot harder to catch up to heat that way.
It's still a work in progress, because everything about Eovaldi is. He's been talking about supplementing his fastball with other pitches since he arrived in New York last winter, and his 13-2 record is far more a result of excellent run support (5.71 runs per game with the Yankees, up from 3.39 with the Marlins last year) than it is about marked improvements in his performance. After all, Eovaldi's ERA and FIP are almost identical to what it was in 2014, when he went 6-14, and that's a great example of why pitcher win/loss record isn't that helpful.
But when the Yanks acquired Eovaldi, they didn't expect a finished product. They expected a 25-year-old with big league experience and a huge arm who still needed to find that last component to become a regular contributor. It's too soon to say that the split is definitely it, because Eovaldi has been throwing it for less than a year and has already changed it once. It sure is a step in the right direction, though, and for a team that is now a half-game behind Toronto in the American League East after CC Sabathia left with an injured knee on Sunday, it's one they desperately needed.