For Eovaldi, the problem isn't with control, as one might expect from a young pitcher who throws so hard. With Miami last year, his 5.0 percent walk percentage was the same as Felix Hernandez and Stephen Strasburg. This season with the Yankees, Eovaldi's 5.5 percent mark is better than Clayton Kershaw or David Price. The problem, instead, is hittability, to the point that no National Leaguer allowed more hits than the 223 he did last year.
Just look at how poorly Eovaldi has fared on getting swinging strikes on his blazing fastball over the last two seasons, compared to all pitchers who threw at least 200 pitches:
2014 -- 5.44 percent swinging strikes -- 80th overall
2015 -- 4.66 percent swinging strikes -- 115th overall
Why is such a hard fastball so unimposing? In part because Eovaldi's spin rate is so unremarkable in either direction. It's not as simple as "more spin equals better pitch" so much as it is that low-spin fastballs tend to get higher ground-ball rates, and high-spin fastballs generally result in more swings-and-misses. Eovaldi's 2,146 RPM four-seamer, which through the end of May had the 272nd-highest spin rate of 409 pitchers who had thrown it at least 40 times, is neither. Fastballs work best at the extreme edges of spin rates, not quietly in the middle.
Now, not getting swinging strikes on the fastball isn't in and of itself a bad thing. Gerrit Cole, another hard-throwing righty, is at only 5.74 percent swinging strikes on his four-seamer this year. The difference is that he has other weapons, almost using his fastball more as a way to set up the hitter than to use it as the out pitch itself. Cole's slider has a 17.95 percent swinging strike rate this year, better than the MLB average of 13.44 percent.
Eovaldi hasn't had that. His slider is a capable second pitch, but it is much more effective against righties (hitting .230 off of it since the start of 2014) than lefties (.310). Eovaldi's curve isn't a weapon, thrown only 9.8 percent of the time since last year, and mainly early in the count. He has long been aware of the need for a third pitch, so in 2012, he briefly toyed with a cutter, but discarded it. Every now and then, a changeup would appear. Last year, Eovaldi first tried a splitter late in the season.
Eovaldi has kept the splitter around this year, throwing it 72 times and allowing only three singles off of it, throwing it primarily when he's ahead in the count as he tries to gain comfort with the pitch. As he told MLB.com's Bryan Hoch this week, "I've been working on it. I've definitely built up a lot more confidence in it, the last few outings."
Interestingly enough, the pitch has the single lowest spin rate (737 RPM) of any non-knuckler thrown at least 40 times this year -- a fact that Eovaldi admitted to Hoch that he "had no idea" about -- and as you'd expect, it's become an easy pitch to pound into the ground. To wit: 92.9 percent of all the Eovaldi splitters that have been put into play have turned into grounders.
With a 4.40 ERA, Eovaldi is still frustrating, despite the big fastball. The slider is still useful; the splitter is still a work in progress. As Eovaldi said, "I've been using it … just because it gets them off my fastball." A 95 mph fastball that occasionally touches triple digits can get you pretty far in this game. But it won't make you a star, not without something else to keep hitters off the scent. As Eovaldi continually looks for that third pitch, the splitter seems like it's his best chance yet.