I can’t think of a way for Mitch Keller to end his 2020 season with more promise, and yet also with more concern.
Keller allowed zero hits in his final 11 innings of the season. He also walked ten batters in 11 innings, including eight in five innings last night.
As he was coming up through the minors, Keller’s biggest strength was his fastball command. He could throw the pitch for strikes, dot the edges of the plate, and generally worked exclusively off the pitch at the lower levels.
His walk rate started to rise in Double-A, and stayed high in Triple-A. He went from the 4-6% range in A-ball to the 8-9% range in Double-A and Triple-A.
The Pirates have seen some exceptionally high walk rates this year from some of their other pitchers. Joe Musgrove has a career 5.9% walk rate, but is at 10.6% this year. Chad Kuhl saw his rate go from 8.8% in 2018 to 14.2% this year. Trevor Williams entered the majors with an 8% walk rate, dropped down to 6.9% last year, and went back up to 8.3% this year.
This is such a crazy year that I wouldn’t put too much stock in the results. But when it comes to Keller, there has been a trend since before this season, and it got worse instead of improving.
His pitches reveal some alarming trends this year. The biggest one is that none of them had over a 13% swinging strike rate. His slider reached that mark, and was the only one over 6.5%, with his fastball being second.
Hitters were largely laying off pitches outside of the zone. The slider got some chases, with a 26.9% outside swing percentage, but the fastball was at 17.4%, while getting contact 84.2% of the time.
By comparison, Gerrit Cole this year had a 27.8% chase rate on his fastball, and a 66.2% contact rate. His slider had a 41.4% swing rate outside the zone, and a 36.9% contact rate. Cole had three of his four pitches with a 16.4% swinging strike rate or better, with his fastball trailing at 11%.
Cole is a lofty comparison for any pitcher, as he’s become one of the best in the league. But let’s not forget that Cole was far from an elite pitcher in his final years in Pittsburgh. Keller has largely been developed under the same system, and I’m not sure how much change could have been made in a shortened 2020 season that was also shortened further for Keller by an injury.
I draw the comparison to Cole because the Pirates need Keller to be a top of the rotation guy if they want any chance at contending over the next few years. I also draw the comparison to Cole because I feel that Keller can be a top of the rotation guy — maybe not to the extent that Cole has become, but definitely a guy who can dominate.
The question is whether the new Pirates’ pitching system can get him anywhere close. So far there have been some good signs, and some concerning signs. We’ll look to 2021 to see which signs remain, and to see how much Keller can improve under hopefully a more normal season.
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