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Nathan Eovaldi needs to understand who he is as a pitcher

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A few months in, the production still isn't there for Nathan Eovaldi. To get to the next level, he needs to begin to understand himself as a pitcher.

Kyle Terada-USA TODAY Sports

For years, Nathan Eovaldi has confounded scouts with his inability to strike batters out in spite of his triple digit velocity. Among the various explanations for this phenomenon, Mike Petriello at MLB.com probably hit the nail on the head when he talked about the spin rate of various fastballs. The spin rate of Eovaldi's fastball is not that great, and a higher rotations per minute value actually correlates better with whiffs than velocity.

The short explanation, with limited physics references, is that a fastball that spins more resists gravity more. Those "rising" fastballs thrown by pitchers like Koji Uehara and Max Scherzer have very high spin rates. That brings us to Eovaldi's "four seam fastball." Here's a heater that he threw to Washington's Clint Robinson, which was hit for a double:

That's a sinker. Every pitch tracking company in the world can categorize that a four-seam fastball, but looking at the movement, it's a sinker. As great as companies like Pitch F/X are, sometimes machines and algorithms are no match for a pair of human eyes. Not only does Eovaldi's lower spin rate lead to less "rise" on his heater, his ¾ arm slot also leads to some more of that extra drop at the end.

Therein lies the issue. Nathan Eovaldi is not just a high velocity pitcher. He is a high velocity pitcher with a low arm slot who doesn't get that much spin. According to Brooks Baseball, Eovaldi has averaged -6.3 inches of horizontal movement and 7.9 inches of vertical movement on his fastball this season. Looking at Baseball Prospectus's leaderboard, those figures fit a lot better in the "sinker" tab, rather than the "four seam" tab. Here's how Nathan Eovaldi has used his fastball in 2015, courtesy of Baseball Savant:

If someone told Eovaldi that his fastball was really a sinker, he would almost certainly make an effort to throw the ball lower. To reiterate, he throws this pitch with a four-seam grip. But because of his low arm slot and his low spin rate, it moves like a sinker. All of which begs the question: what could he do with an actual two-seam grip?

According to Brooks Baseball, Eovaldi tried to throw a two-seam fastball in 2012, while he was a member of the Marlins. For whatever reason, he basically scrapped the pitch after that. He was probably hoping to focus on commanding his four-seam fastball. But at that point, he was throwing at a slightly higher arm slot. At his current low ¾ delivery, he would probably generate a significant amount of sink if he threw with a two-seam grip.

The St. Louis Cardinals' fireballer Carlos Martinez also throws from a ¾ arm slot and gets about eight inches of vertical movement on his four seam fastball. His two-seamer actually drops so much that it generates a very good 11% whiff rate. If Eovaldi can develop a two seam fastball, there shouldn't be any reason why he can't do the same. It will be tough at first. Commanding his four seam fastball has been enough of a challenge by itself. But Eovaldi is still a work in progress. The Yankees knew that when they traded for him. The fact is that when it comes to his development, there is much more than just the number on the radar gun.