Robert Gsellman of the New York Mets had a fairly average 2018. After struggles in the rotation during 2017 due to injury and ineffectiveness in facing batters a third time, as well as losing two miles per hour on his sinker compared to the previous year, Gsellman was moved into the bullpen full time. The plan initially worked, with an uptick in velocity and an improved strikeout percentage during April. Unfortunately, the rest of his season was filled with highs and lows, resulting in an 86 ERA+. However, his curveball did improve drastically in 2018.

Changes to Movement

One of the main ways Gsellman’s curve improved was his added spin rate. In 2017, his curveball had 2606 revolutions per minute, and in 2018 it was 2699 rpm. An increase in spin rate leads to an increase in the movement of the pitch. These two graphs demonstrate how this increase in spin rate translated into movement from 2017 to 2018. The first graph shows changes in vertical movement and the second one shows changes in horizontal movement.

These graphs express how Gsellman has added more bite to his curve (vertical movement from -4.3 to -6 inches) and a bit more depth to his curve. Visually, we can see this using the power of GIFs. The first GIF is his curve from 2017 and the second one is from 2018.

The 2018 curve breaks more sharply and also breaks from right to left more, as opposed to its 2017 counterpart, which is more of a tight vertical break. This added spin was most likely due to an increase in the pitch velocity increasing (80.2 mph to 81.8 mph). Read the rest of this entry »