Sluggish Fastball Rotation Responsible for Sabathia’s Rough Start

The match up from Tuesday’s game consisted of a 24 year old , a player on the cusp of being sent down, and  ace . In a reversal of fortune, Minor was nearly flawless in his 7.1 innings of 5 hit ball, while Sabathia allowed 10 hits and 4 earned runs in his 7.0 innings. A lack of fastball control plagued the Yankee southpaw while facing Atlanta, but he was able to escape the game with a spectacular win as and homered for six RBI’s in the 8th inning. It’s quite a feeling when you steal these types of games from such tough teams as the Braves, but despite the uplifting end, I didn’t forget about Sabathia’s rough performance. While the Braves are a strong offensive team, something didn’t sit right while watching them square up fastballs from one of the best pitchers in the game. PITCHf/x has the reason why.

Looking at the four-seam fastball from his 6/12 start, the movement of the pitch and velocity showed signs of deterioration compared to the rest of 2012. The two inches lost in “rising” action (vertical movement), and the inch lost in movement towards right handed hitters, could be a sign of an improper spin angle. At 157 degrees, the numbers show an identical spin angle between this start and his average fastball. The culprit stems from the  400+ rotations per minute lost in Tuesday’s game. The spin of a pitch has a direct relationship with the Magnus effect responsible for movement. In this case, the loss of spin rotation on Sabathia’s four-seam fastball has resulted in a loss of 2 inches of vertical movement, and an inch of horizontal movement. Although there is less of a direct link between spin and velocity, the small loss of .7 mph is most likely due to the same flaw that caused a loss in RPM.

Not only did the decrease in spin lead Sabathia to lose his control, but it also resulted in a fastball that was easier for hitters to elevate. So far in 2012, Sabathia’s four-seam has produced 9.24% groundballs (45%), 4.69% linedrives (23%), and 6.60% (32%) flyballs, which is very consistent with his total batted ball profile this season of 48% groundballs, 21% linedrives, and 32% flyballs. Aside from the fly ball and line drive hits from Tuesday night’s game, Sabathia’s ground ball to flyball outs ratio was 8-7, a jump from his typical flyball numbers. When attempting to produce a desired batted ball, the spin and movement of a pitch is arguably the most important factor in determining the type of contact. Against the Braves, a lack of speed and movement on the four-seam resulted in more elevated hits.

Pictured above are two four-seam fastballs thrown from Sabathia on Tuesday, noted with the rotations per minute. While both pitches were called for in nearly the same down and away locations, the pitch on the left dramatically misses it’s location, while the pitch on the right is nearly perfect. Also notice that the pitch on the right has a spin rotation consistent with his 2012 average, while the pitch on the left has 33% less spin. When watching the mechanics, there appears to be two differences above, the first being slightly more arm speed on the high rpm pitch. Looking at the end of the delivery, you’ll see that the throwing arm in the left picture finishes a split second after the arm pictured on the right. While this could be a fatigue issue, both pitches were taken from the first two innings of the game. The second flaw is in his balance, where he finishes his delivery in an upright position on the high-rpm pitch, but trails off to the right of the mound on the low rpm pitch. Instead of the direct problem, finishing without a proper upright stance may indicate a loss of balance at somepoint during the delivery.

Unfortunately, mechanical flaws exist in every start for every pitcher, and there is no way of telling if these balance and arm speed issues were responsible for the low RPM pitches. Sabathia claimed that the same control problems he’s faced all season manifested themselves on Tuesday, but the numbers show that a much deeper mechanical flaw came out for this start. This occurrence of low rpm is an outlier compared to the rest of his starts, and there is a good chance we won’t see these types of problems continue. Still, I’ll be keeping an eye on the spin rotation during his next start on Monday.