One of the savvy moves the Oakland A’s made this February was signing backend bullpen piece Trevor Rosenthal to an oddly structured one-year deal. While Rosenthal can potentially provide some serious firepower out of the bullpen, his recent mild groin injury is a reminder that the veteran right-hander has had issues staying on the field as of late. It seems that this injury isn’t too serious, but if Rosenthal’s health keeps him off the field or his stuff isn’t working as well as expected, the A’s aren’t without hope. They have Jake Diekman!
Diekman was acquired by the A’s from the Kansas City Royals at the 2019 trade deadline. The transaction was simple: a competing team bolstered their bullpen with a decent middle reliever. Diekman didn’t light the world on fire with his 2019 performance, but in a shortened MLB season, Diekman truly shined.
Jake Diekman looking to replicate his impressive 2020 campaign
The A’s laid claim to the best bullpen last season, and it was a critical component to their division title. AL Reliever of the Year Liam Hendriks deservedly got much of the attention for the bullpen’s success, but Diekman also threw incredibly last year. The 34-year-old veteran only allowed one earned run and struck out 31 batters in the 21.1 innings that he pitched. Most people will look at Diekman’s 2020 season and say, “Well, that certainly isn’t sustainable.” Of course, those people are correct, but there is reason to think that Diekman might have his best full 162 game season in 2021.
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Diekman has had to pitch in rough situations throughout his career. He played his first three and a half seasons in Philadelphia, which was not a desirable place to be a pitcher in the early 2010s. The Phillies put out some of the worst defenses in the league, finishing in the bottom five in DRS each year Diekman was on the team.
After a short, rough stint in Arizona, Diekman arrived at his next long-term destination, Arlington. While the Rangers were able to put better defenses behind their pitchers, the now-retired Globe Life Park in Arlington at times played like a little league park. The hot Texas weather encouraged loud contact, and fly balls that found the notorious jet stream magically turned into home runs.
Many of the hurdles that Diekman has faced on previous teams are no longer issues in Oakland. He has two Gold Glove winners and plenty of other sure-handed defenders behind him. Diekman also gets to pitch in a ballpark that is one of the most forgiving in baseball. Diekman has thrived in the Coliseum, only allowing five runs in 31.1 career innings, and he has yet to give up a home run in the city of Oakland.
It is no secret that Diekman has a walk problem. The lanky lefty has posted a walk rate under 10 percent only once (in the long time ago of 2014) and is frequently in the bottom 5% of the league in that stat. It’s unlikely that Diekman will rob Greg Maddux of his command Monstars style, but with a little more help from defense and his environment, the exciting components of his game can stand out more.
Even though the ERA wasn’t impressive in 2019, the Nebraskan started missing more bats that year. He was getting more hitters to chase, and his whiff percentage went up 7 percent. All of his expected stats (xBA, xOBP, xWOBA) started looking less like the numbers of a valuable middle-inning reliever and more like a guy you would want out on the mound with the game on the line. 2020 saw a continuation of this trend; he finished at least in the top 98 percentile in the expected stats, strikeout percentage, and whiff percentage.
Another element of Diekman’s game is his ability to keep the ball in the ballpark. While his walk numbers are very low on leader boards, his home run numbers are equally outstanding. Combining his 2019 and 2020 seasons, Diekman is 4th in HR/9, behind elite reliever Kirby Yates and sinker master Zack Britton (Min 40 innings pitched).
It’s been a treat to see Jake Diekman flourish in Oakland late in his career. You might think that a high walk, high strikeout player would be more park and fielding independent, but I look at it another way. With as much traffic as Diekman allows via the walk, he needs every single element of his game to be unimpeachable. A ball that gets past a poor fielding third baseman or a ball that cleared the fence due to hot weather is much harder to deal with if there are men on base.
Jake Diekman still needs to prove that his swing and miss ability is truly elite, but with his late-career swing and miss surge coupled with good defense and a big park, I would feel confident giving him a chance in the closer role.