Thorburn: A mechanical look at the pitchers who lost the most fastball velocity last season

From Doug Thorburn at Baseball Prospectus on March 3, 2014:

When it comes to pitching, velocity is the straw that stirs the drink. Fastball speed provides the baseline for batter timing and sets up every other arrow in a pitcher’s quiver, explaining why velocity is the most sought-after commodity in pitchers at every level of play. Consequently, it can be devastating when a big-league pitcher transitions from pumping premium octane to regular gas, as it slows the performance of the whole machine.

Thanks to the bounties of PITCHf/x and sites such as, we have the ability to monitor a pitcher’s stuff over the course of multiple seasons. We expect that velocity will diminish over time, and that a pitcher must hone the finer elements of his game in order to sustain the performance of his youth. With this concept in mind, let’s examine the pitchers who cooled down significantly last season and take a look under the hood to better understand the causes behind their downgrades.

First, the ground rules: We are looking at the three-year period from 2011-13. Each of the pitchers in the charts below suffered at least a half-mph drop from each of the previous two seasons to 2013, as well as the loss of a full tick from at least one of the two years under the microscope to 2013. In order to qualify, a pitcher had to throw at least 500 pitches that qualified as fastballs or sinkers in each of the past three seasons. The numbers in the charts were calculated based on a weighted average of the pitch-speeds of four-seam fastballs and sinkers in each season.

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Originally published: March 3, 2014. Last Updated: March 3, 2014.