Where did their Spin go?

Usually when a pitcher adds more spin to his fastball you see a relatively similar increase in velocity; however, these 5 pitchers go against this pattern drastically.  I looked at 5 pitchers’ fastballs who have lost 100 or more RPM this year compared to their 2020 data, while also showing an increase in velocity.  These 5 pitchers are Robbie Ray, Taylor Clarke, Lucas Sims, Cam Bedrosian, and Connor Brogdon.

To look more at the relationship between spin rate and speed of a pitch, Bauer Units was introduced.  A pitcher’s Bauer Units will typically stay relatively consistent as they gain or lose velocity and spin through their career. I compared all the pitchers who threw to at least 25 batters in 2020 vs. 2021.  In 2020, the average spin rate for pitchers was 2276 and the average velocity was 93.08 MPH.  Both these are a tick-up in 2021 with the average spin rate for pitchers being 2298 and velocity of 93.31 MPH.  These ratios are almost equal in terms of Bauer units as 2020 pitchers had 24.5 compared to the 24.6 in 2021.

Above are each of these 5 pitchers’ fastballs using BallR

These 5 pitchers have all seen a large drop in Bauer Units this year, averaging a 1.6 point decrease.

This chart is updated as of May 12th, 2021 and compares vs. pitchers’ 2020 data
Taylor Clarke overlay of Fastball (Maroon) and Slider (Gold) vs. Fernando Tatís Jr.

Taylor Clarke (seen above) has had the biggest dip in spin rate of his fastball going from (2336 RPM) in 2020 to (2150 RPM) in 2021.  What is so strange, is that he has gained 1 MPH in his fastball’s speed while losing all this spin.  I figured maybe his release could be changed or his spin efficiency, but his fastball spin direction is the same for both years at 12:45.  In addition his active spin is almost identical showing 90% in 2020 and 91% in 2021.  Furthermore, his fastball vertical movement has only changed by 0.2 inches and his horizontal movement has only changed by 0.1 inches.

Interestingly, 4 of the 5 pitchers who have seen this drop in spin with increase in velo have seen a higher whiff% on their fastball. Overall, their collective whiff% increased by 5.2%, from 21.5 to 26.7. Looking at xwOBA though, 4 of the 5 pitchers have seen worse numbers on their fastballs this year.  Collectively their xwOBA of their fastballs has increase from .329 to .367.  These two statistics seem to contradict each other because a higher whiff% is better for a pitcher, but a higher xwOBA is worse for a pitcher.  Of course, a larger sample size for these pitchers would be better as well as more pitchers who follower this pattern to see if the results hold true.

If anyone has any explanation on how these pitchers could have lost so much fastball spin while gaining velocity, I would love to hear it!

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