Nick Nelson could rise up in the Yankees’ bullpen

Nick Nelson played at all three levels of the Yankees’ minor league system in 2019, but the lack of a minor league season this year created question marks for where his progression would lead him in 2020. As it turned out, Nelson impressed enough to make his major league debut, wound up appearing in several games and even cracked the postseason roster.

Overall, the numbers didn’t show a particularly impressive pitcher: he had a 4.79 ERA, a 5.56 FIP and a 4.45 xFIP, with 7.84 K/9, 4.79 BB/9 and 1.74 HR/9. He was both walk and homer-prone, which is not a good combination in major league baseball.

However, his final line was tainted by a terrible outing on August 5. That day, against the Philadelphia Phillies, the Yankees needed some outs because they were short on arms, and left Nelson on the mound on mop-up duty despite the fact that he was being hammered by the Phils. He allowed six runs on seven hits and a walk in 1.2 frames.

If we take away that outing, Nelson ends 2020 with a 2.37 ERA, albeit with a still mediocre 10/18 BB/K ratio. There is clearly work to be done here, especially with control and the command of his pitches. But if the Yankees play their cards right, Nick Nelson could be their next impact reliever.

Why am I so high in Nelson? Well, he throws some serious heat, averaging 96.3 miles per hour with his four-seamer. He has great active spin numbers as well, despite being in the 13th percentile in overall spin rate with his fastball.

Active spin vs. inactive spin

Why the disparity? Here is MLB definition of spin rate: It represents “the rate of spin on a baseball after it is released. It is measured in revolutions per minute. The amount of spin on a pitch changes its trajectory. The same pitch thrown at the same velocity will end up in a different place depending on how much it spins.”

However, there are two types of spin: gyroscopic, or inactive spin; and active spin, as Ben Clemens of Fangraphs’ kindly explains here while analyzing Dylan Cease of the Chicago White Sox. Active spin is the one that impacts ball movement, while inactive spin is mostly useless from that perspective.

Cease ranked in the 94th percentile in fastball spin, but only 75.2 percent of that contributed to movement of the pitch, ranking 331st out of 399 qualifiers. That resulted in a very hittable fastball and a low 17.2 whiff percentage on the pitch.

Nelson, in 2020, was in the 13th percentile in overall spin rate, but ranked 131st out of the 399 qualifiers in active spin, with 90.8 percent. This “rising” effect was in full display on an August 1 outing against the Red Sox in which he hurled three scoreless innings with no hits, a couple of bases on balls and four punchouts.

“You saw the high-velocity fastball really playing up at the top of the zone,” Yankees manager Aaron Boone said back then.

What do the numbers say?

Nelson ranked 75th out of 409 pitchers in percentage of fastball “rise” vs. the average, with 10%. In total, his heater had 12.5 inches of vertical movement (47th out of 409), or 1.4 above average.

Now, Nelson’s fastball was hammered for a .314 average and a .341 expected average. Batters had a .447 wOBA and a .458 expected wOBA, coupled with a 92.1 average exit velocity and a rather mediocre 22.3 whiff rate. What does that tell me? While he seems to have the goods (the velocity and the active spin), it is a matter of improving his command to truly make the leap.

Both his changeup and slider were decent, producing over 30% of whiff rates and under .300 of xwOBA. If he manages to master the art of using the rise on his fastball and consistently locating it up in the zone without leaving it on the fat part, and he trims the walks somewhat, he could take off. At the very least, he presents an interesting project for pitching coach Matt Blake now that he will have a normal offseason and some big league experience.