Koehler has a good looking fastball he can throw for strikes, keeping it in the zone 51% of the time and getting up to 95 mph on the gun (though he’s gotten as high as 97 mph before). He’s expected to be a bullpen arm this year and that velocity should go up with the move. However, he doesn’t get batters to swing and miss (only 5.1% whiff rate) and he did give up a .346 wOBA against.
His curveball was a bit worse this past season, as he wasn’t getting batters to chase the way they had in the past, as his O-Swing rate dropped from 37% to 25%. His swinging strike rate was also the lowest it’s been in four years, sitting at a mere 8%. He does get a lot of ground balls with his curveball though, at over 60% for his career on the pitch.
The slider has always been Koehler’s chase pitch, with a career O-Swing rate of 41% and swinging strike rate of 17.9%. Unfortunately, his home run rate skyrocketed on this pitch in 2017, jumping from his 9.1% career mark to 25%. That was the main reason his slider was so ineffective this season, and if he can limit the damage batters do on it, it can be his best pitch again.
Despite throwing it out of the zone nearly two-thirds of the time, Koehler was able to throw his change ups for strikes as he got batters to chase on it over 40% of the time. He did give up a 1.200 OPS against though, and this pitch has been consistently hittable over his career (.835 OPS against). His usage of the changeup has declined, and it looks like a distant fourth option at this point.