Understanding Rapsodo Pitching Data: Spin Rate & Efficiency Profile (Curveball, Slider, Changeup)

Curveball

Curveballs and sliders typically will register the highest raw spin totals of all pitches (MLB average spin rate ≈2430-2530 rpms), though these ranges can become more inflated based on the gyroscopic  spin measurements  of each pitch. Spin rate will obviously play a part in the overall movement of these breaking pitches, but their spin efficiency profiles are very different.

12-6  curveballs  should spin  opposite of four-seam fastballs. These curveballs are typically thrown with less spin efficiency than those fastball  types  (MLB average was around 78%); increased efficiency will increase the vertical drop of the pitch, thus making them a great complement to “rising” four-seam fastball. In order to best utilize the topspin profile of the pitch, gyroscopic spin should be minimized as much as possible.

Sweeping curveballs, as their name implies, should have higher horizontal break measurements (i.e. sweep) than vertical break.   In order to achieve this without the pitch acting more like a sidespin slider, spin efficiency needs to  be  kept at least between 65-75% (MLB average ≈ 68%) while also being thrown with an 8:00-9:00 spin direction. These curveballs pair well with low-slot pitchers who possess heavy fastballs or fastballs with depth and above average run.

Slider

Sliders should maintain the highest gyro degrees and lowest spin efficiencies  in a given  pitcher’s entire repertoire. This holds true across the board for the three different slider classification listed on our  MLB Data Guide, as sliders require more gyroscopic spin in order to be effective.  

As can be implied by their classification title, gyro sliders need to have spin efficiencies lower than 10%. This allows the velocity, pitcher’s release point, grip, gravity, and partial sidespin imparted on the ball to dictate the ball’s movement pattern. 

Topspin and sidespin sliders can be thought of as siblings to cutters and sweeping curveballs, respectively, albeit with lower spin efficiencies (roughly 35%) and higher gyro degrees (65-75). Topspin sliders generate more depth than gyro and sidespin sliders, while sidespin sliders generate greater sweep than its contemporary. Pairing the right slider type is highly dependent on the pitcher’s goals and current spin-induced movement matrix between his other pitches. 

Changeup

The two major goals of changeups should be to maximize the velocity differential off the fastball and minimize vertical break as much as possible. While reducing spin efficiency can definitely minimize vertical break, feel for the pitch as well as the pitcher’s primary fastball play a major role in determining the correcting offspeed pairing. 

In the table below, we see four distinct offspeed pitch types whose movement profiles are directly linked to their respective spin rates and spin efficiencies. Pitcher A’s low spin rate and near-perfect spin efficiency give his offspeed offering more of a tumbling effect; this pitcher would need to have 20+ inches of vertical break on his fastball in order for this changeup to be effect. Comparatively, Pitcher B’s higher spin rate and lower spin efficiency will lead to better fading action. The lefties, Pitcher C and Pitcher D, have relatively similar spin rates and spin directions, but Pitcher C’s perfect spin efficiency is able to generate a greater amount of arm-side run and “frisbee” action, while Pitcher D’s lower spin efficiency gives him similar fade to Pitcher B.