Spin rate, or raw spin, measures the overall revolutions per minute (rpm) of a pitched ball by adding together the amount of backspin, topspin, sidespin, and gyroscopic spin (i.e. bullet spin, football spiral, etc.) put on the ball.
A popular buzzword amongst the wider baseball community, spin rate has grown to become a key differentiator between average and plus-to-elite offerings. Spin rate has even been deemed so important that a new method of measuring pitches relies on it; Bauer Units – yes, that Bauer – take the spin rate of a given pitch and divide that measurement by the velocity of said pitch.
We will not be totally focusing on that here today, though it is a measurement Rapsodo offers in our updated Bullpen Reports.
While raw spin does tell us how well a player is able to physically spin the baseball, relying solely on raw spin does not explain the entirety of the ball’s path to home plate.
This is where True Spin comes in to play. One of the largest differentiators between Rapsodo and other consumer ball flight tracking technologies is Rapsodo’s ability to track both raw spin and the percentage of raw spin that directly impacts movement. This measurement is called spin efficiency.
When a pitched ball’s spin efficiency is multiplied by raw spin, we are given the True Spin of the ball. Knowing the True Spin of the ball allows both player and coach the opportunity to understand how much spin is directly impacting the ball’s movement profile.
Some of you may be scratching your head and asking yourself, “But why do you need True Spin? Wouldn’t more spin equate to more movement?”
The first three types of spin I listed at the beginning of this article – backspin, topspin, and sidespin – all directly affect how the ball reacts to natural forces as it travels through the air. Higher measurements of these will indeed increase induced movement.
Gyroscopic spin has very little impact on pitched ball movement other than propelling the ball towards home plate; to best illustrate this, think of a football thrown with a perfect spiral. This does not necessarily make gyroscopic spin something to avoid, but rather something to be aware of in the pitch development and design process.
Here are the other articles specific to each pitch type and spin rate and efficiency profile :