In 2015, Doug Fister posted one of the worst seasons of his career. He managed to pitch only 103 innings, his home run rate spiked, he wasn't generating as many ground balls as he used to, and his fWAR was tied for the lowest value of his career. That's pretty clear-cut.
Fister suffered a steep decline after his 2013 and 2014 seasons, and at 31 years old, it would seem a little early to attribute all of his struggles solely to his age. Instead, it appears that the cause for his downfall is related to his declining two-seam fastball.
For the first time in Fister's career, his two seamer had a negative pitch value, which was likely driven by his declining velocity and horizontal movement.
From 2014 to 2015, Fister lost as much horizontal movement as he did from 2011 to 2014. As a result of the declining velocity (down 1.7 MPH) and effectiveness of his two seamer, Fister began to pitch differently with it.
For the 2014 season, Fister threw 63.1 percent of his two seamers on the inner half, but in 2015 that figure decreased to 59.4 percent. With the loss of movement on that pitch, it appears that Fister became less confident in throwing it inside to right-handed hitters, as it was no longer breaking in toward them as much. His horizontal release point also became an issue.
While there isn't a drastic change between his 2014 and 2015 release point, the further loss of movement on his two seamer exacerbated the issue. By moving his arm closer to the plate (horizontally so), coupled with the declining horizontal movement, Fister's two seamers became more vulnerable. Batters sprayed the ball all over the field.
Unfortunately for Fister, he wasn't generating as many ground balls as normal, and in 2015 his two seamer was frequently hit into the outfield. In the last two seasons, while he allowed the same number of home runs (eight) off his two seamer, they came much more frequently this year than ever before in his career. His homer per fly ball rate increased to 19.5 percent from 12.3 percent last year and 7.5 percent in 2013. In addition to the increased homers, Fister's line drive rate allowed on the two seamer was at 30.4 percent, a career high. It was much easier to make solid contact against the pitch in 2015 than in previous years.
Fister's downfall couldn't have come at a worse time, as he's now a free agent coming off arguably the worst year of his career. His declining velocity is a red flag, and he might have to rebuild his value on an incentive-laden one-year deal. There could still be hope for Fister; by changing his horizontal release point and moving closer to right-handed hitters as well as decreasing his usage of the pitch (usage came in at 63.3 percent, the highest of his career by far), he could compensate for the loss of horizontal movement and potentially regain some of his value.
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Matt Goldman is a Featured Writer with Beyond the Box Score and a Contributing Editor at MLB Daily Dish. You can follow him on Twitter at @TheOriginalBull.