Up until a few years ago, throwing a baseball was never about improving spin rate or axis. The capability to measure either just didn’t exist: large data sets were used to assess broad trends in player performance. But with the increasingly accurate methods of measuring player movement analytics, understanding the physics of a pitched ball are giving front offices, coaches, and teams the ability to hone and improve their pitchers.
Spin rate and spin axis are two attributes of a thrown ball that can be precisely measured with the digital technology available in today’s era. The spin rate primarily influences the vertical motion of a baseball as it travels from the pitcher’s hand toward the batter. Spin axis affects the direction that the ball takes when moving between pitcher and hitter. Taking a closer look at spin rate and axis are crucial to understanding what separates great pitches from average ones.
Spin rate is directly related to the amount of vertical movement of a pitch. It is the measure of the number of times a baseball spins after being thrown. Balls that are thrown with the same velocity but different spin rates will end up in a different place from the pitcher’s hand to when they reach the catcher’s mitt.
Fastballs are affected by spin rate, with a higher rate usually resulting in a ball that will rise as it nears home plate. A high spin fastball rises as it reaches the catcher, resulting in more swinging strikes or fly balls. But a skilled batter can turn a high spinning fastball into a home run.
Unsurpisingly lower spin rate works in the opposite way. Low-spinning fastballs drop in the strike zone as they reach the plate, resulting in more contact and a greater prevalence of ground balls. When you hear the term “ground ball pitcher”, it usually indicates an individual with a low spin rate on their fastballs.
So what are spin axes and how do they relate to spin rate? The spin axis is controlled by the hand and finger positioning at the point the ball is released by the pitcher. Put another way, spin axis is how the ball rotates in 3 dimensions.
The combination of spin rate and spin axis is what determines the movement of a pitched baseball.
Understanding Your Spin Rate
There is some controversy over how much a pitcher can change their spin rate. Some Major League pitching staffs, notably the Houston Astros, seem to allow pitchers to raise their spin rate. This may just be a result of a greater emphasis on throwing fastballs as opposed to other pitches, as suggested by Gerrit Cole when explaining his increased spin rate after joining the Astros.
From a pitcher’s and manager’s perspective, understanding spin rate and axis can help in developing real-time strategies for opposing hitters. If you need two outs, you want a pitcher with a lower spin rate to get a ground ball and a double play. Pitchers who understand the movement of their pitches can use that knowledge to fool a hitter. Spin rate and axis, metrics inconceivable to the game only a few years ago, bring pivotal information that are changing the ways teams prepare, players train, and fans enjoy professional baseball.