The Career of Jake Diekman

The Boston Red Sox bullpen received a boost in the form of left-hander Jake Diekman. The Red Sox signed Diekman to a two-year, $7 million deal. The 35-year-old veteran is coming off the 2021 season with the Oakland Athletics where he put up a 106 ERA+ and 1.335 WHIP in a little over 60 innings pitched. He’s also spent time with the Philadelphia Phillies, the Texas Rangers, and the Kansas City Royals.

To give us a better look at who Diekman is we are going to look back at his career, and what his pitch arsenal consists of, much in the same way we did with Chris Sale. We’ll analyze everything from his first pitch with the Phillies in 2012 to his latest pitch with the A’s in 2021.


Diekman debuted for the Phillies on May 15, 2012. Against the Houston Astros, he pitched 1 1/3 innings and struck out three, while also earning the win. It was an impressive start for a career that has lasted over a decade and counting. The rest of that year was a mixed bag. That year he faced 131 batters. On the positive side, he finished with an above average ERA+ of 103 and a 11.5 K/9. On the down side, he had a hard time with control, and that showed with his 6.6 walks per nine and his 1.646 WHIP. All in all for a rookie, that’s not a terrible start.

Diekman’s best full season was arguably as a member of the Rangers in 2016. In 53 innings he had a 135 ERA+, and accumulated a full season career best 1.1 WAR. Diekman also balled out during the shortened 2020 season. In only 21 and 1/3 innings, he racked up 1.5 WAR with a 0.42 ERA, 1003 ERA+, and 0.938 WHIP.

Righty Killer

Diekman is unique in the fact that he is a lefty that is more effective against righties than he is against lefties. For his career, righties have a slashline of .212/.323/.344 compared to .232/.342/.310 against lefties. He’s faced a total of 1250 right handed batters and 755 left handers over the course of his career. In 2020 and 2021, Diekman was .135/.236/.245 against righties. In a division that features the likes of Vladimir Guerrero Jr., Aaron Judge, and Giancarlo Stanton, Diekman provides an interesting wrinkle in the Red Sox’ bullpen.

Diekman’s Career Righty Splits

Pitch Selection

Looking at the plot below, we can see that starting in 2016 Diekman began to introduce his 4-seamer. Now this pitch is his primary pitch, and his sinker has taken a continuous dip. Currently Diekman features a 4 seamer, slider mix and the sinker serves as his tertiary option.

Swing & Miss Percentage

Diekman’s slider has the highest swing and miss percentage, and is especially tough against righties. His slider induced a .121 batting average and .303 slugging percentage and a .219 WOBA.


Diekman will be expected to be a key part to the Red Sox’ bullpen that serves to be affective against both right and left handers. This addition also builds depth in the back of the bullpen that was a problem area for the club last year.


Main Photo:

Embed from Getty Images

Players Mentioned:

Jake Diekman, Chris Sale, Vladimir Guerrero Jr., Aaron JudgeGiancarlo Stanton