Kendall Graveman's Improved Slider Has Made Him An Effective Reliever

Kendall Graveman is a different pitcher now.  I mean, he's an Astros today after being traded yesterday afternoon. The oddness of players being traded to the team they are playing was a major theme of yesterday's game, as Joe Smith and Abraham Toro played for the Mariners (and then presumably went back to the Astros team hotel...I'm pretty sure they were traded after check out time). 

Graveman touched on his mixed set of emotions in a pre-game session with media from both Houston and Seattle. 

An emotional Kendall Graveman was shocked to be traded from Mariners but excited for new opportunities with the Astros pic.twitter.com/3lVaMizuvs

— Brian McTaggart (@brianmctaggart) July 28, 2021

But Kendall Graveman is a different pitcher in his pitch mix and approach this season. In particular, Graveman is throwing his slider  harder and more than ever. 

Kendall Graveman in his new duds. 

Graveman, who was part of the package Oakland received for Josh Donaldson in 2014, was in the As rotation from 2014 through a 2018 elbow injury. Graveman sat out 2019 while rehabbing after Tommy John surgery, and signed with the Mariners in 2020. A "benign bone tumor in his neck forced him from a starting role" and into the Mariners bullpen in 2020. But a 5.79 ERA indicated that changes were needed if Graveman was going to remain a major league pitcher. 

Graveman's adjustment was to throw his slider as his primary secondary pitch. Graveman's pirmary pitch throughout his career is a two-seam sinking fastball. He's thrown it for a majority of his pitches every season except 2015. This season he's throwing it on 5 of every 8 piches (63.5%). Graveman also throws his fastball hard, averaging 96.5 MPH on it (which is 90th percentile in the MLB this year).  Like most players, Graveman was able to increase his velocity a couple of miles per hour when he moved to the bullpen and was able to give maximum effort on every pitch without having to worry about pacing himself for later innings. 

For most of his career, Graveman's primary secondary pitch was his cutter. But in 2021, he has not thrown a single cut fastball according to Baseball Savant. Instead, Graveman has ramped up the usage of his slider. 

The chart to the right shows Graveman's slider usage across his career. He threw it less than 10% of the time every season of his career except 2018. But as the chart shows, in 2021, Graveman has increased his usage of his slider, throwing it nearly 20% of the time. 

Graveman is not throwing the same slider that he threw when he was a starting pitcher from 2014 through 2018. The second chart shows the velocity on Graveman's slider. 

When Graveman threw his slider in the rotation, it served as a change of pace pitch. He threw it softly, recording velocities around 80 MPH. But since his move to the bullpen in 2020, Graveman is throwing his slider harder, much harder. He is averaging 87.7 MPH on his slider this season. 

So he's throwing his slider more often and harder. Is it working? 

When it comes to getting swings and misses, the answer is an unqualified yes. Graveman has induced 43 swings and misses on the 94 sliders he has thrown in games this season for a 44.9% whiff rate. In his 5 previous seasons in the majors, Graveman had a whiff rate of 28.4% on his slider. 

But when it comes to actual results, it is not clear that he's improved the results he's getting from his slider. Before 2021, Graveman has recorded wOBAs against his slider of .253, 288., 182, .310, and .000 (10 sliders in 2020). In 2021, he has given up a wOBA of .268 on his slider. While that number is no different than what he has recorded in the past, it shows that Graveman has always had an effective slider. His decision to ramp up its usage this year has keyed him improvement as a reliever. 

Graveman's improvement in 2021 has also been aided by a BABIP of .176, well below the MLB rate of .288. Graveman has give up only 4.1 hits per 9 innings pitched.  Even with the Astros excellent defense, that is likely to rise over the next two months.  

But Graveman also has very good command. He's walked 6.6% of the batters he has faced this season, right in line with the 6.9% rate that he's walked in his career. Despite throwing his slider harder and more often than in the past, it has not lead to more wildness from Graveman. This will be a particular help to the Astros bullpen, which is walking 10.3% of all batters they face, only 17th best in the majors. 

Graveman is a free agent after this season. So this trade is about 2021. In 2021, Kendall Graveman has made adjustments and improvements that have made him a much more effective pitcher. That improvement needs to carry through to October.