In 2019, Diekman replaced his sinker with a four-seam fastball, which ended up being a good decision as he gave up only six extra-base hits in 107 at-bats and a BAA of .215. While it didn’t have quite as much vertical break, its horizontal movement was 5.7 inches above league average. One thing to note is that the exit velocity against the pitch was not great, sitting at 90 mph, which can be explained by its high line-drive rate of 38% (league average is around 21%).
Diekman’s very good whiff rate of 45% with the slider can be attributed to the elite vertical break he generates on it (42 inches, or 5 inches above league average) which naturally led to an above-average O-Swing rate of 38% as batters chased the pitch outside the zone. Its usage was up 10% from last year, which is not surprising, considering the results it was getting as the season progressed.
Despite an overall positive pVal of 1.5, there are a couple troubling factors. 2018 was the fourth consecutive year of decreased velocity on Diekman’s sinker. Diekman has also always struggled with walking batters with the pitch, and 2018 wasn’t any different at 16.9% walk rate.
2018 was the first year that Diekman’s slider has had a negative pVal (-3.5). Diekman has always kept his slider out of the zone, and 2018 was no different, as this was the fourth straight season of sub-30 Zone% at 29.6. The big difference was a drop in SwStr% and the corresponding K%. After being higher than 50 K% for every season except the injury-shortened 2017, 2018 brought a 35.5%.