On February 1, the New York Mets were reportedly close to an agreement with left-handed reliever Jake Diekman. The following day, it was confirmed that New York and Diekman were in agreement on a one-year deal worth $4 million that also contained a vesting option for 2025. The vesting option will be triggered if he pitches in 58-or-more games during the 2024 season.
By adding Diekman, the Mets continue to solidify a bullpen that, on paper, is looking much more effective than it did entering the team’s troublesome 2023 season. With Diekman projecting to be another top left-handed option, behind Brooks Raley, what exactly can Mets fans expect to see from the former Philadelphia Phillies draft selection?
Diekman, 37 years old, has spent parts of 12 seasons in the big leagues. After seemingly revitalizing his career in 2021 with the Oakland Athletics, 0.42 ERA over a 21 1/3 inning sample size, he regressed in 2022 (4.99 ERA and 5.00 FIP) and ultimately was designated for assignment by the While Sox in 2023 after posting a 7.94 ERA across 11 1/3 innings. After being placed on unconditional release waivers, the Rays took a shot on the veteran and it paid off in a big way to end the 2023 season.
In all, Diekman ended up appearing in 50 games, throwing 45 1/3 innings for Tampa Bay last season. He posted a starling 2.18 ERA to go along with 53 strikeouts. Diekman also saw his walk rate plummet from 10.3 walks per nine innings with the White Sox in the beginning of the season to 5.0 and strikeout rate increase from 8.7 per nine innings to 10.5. His hard-hit rate also decreased from 32.4% to a career-low 26.0%. The 26.0% mark would have ranked around the league’s 99th percentile.
Jake Diekman. Photo by Nathan Ray Seebeck-USA TODAY Sports
Well, why did this happen? It is said that Tampa Bay was able to tweak Diekman’s delivery in a way that decreased walks and increased his command. The evidence of the change in walks was mentioned above, decreasing by 5.3 walks per nine innings. In return, Diekman saw increases in strikeouts, softer contact being allowed, and he was able to finish the season as one of the best left-handed relievers in the game.
Worth pointing out, although better, the 13.5% walk rate he posted during his stint with the Rays is still very high. Granted, that figure is much more in line with Diekman’s career average, but is much higher than the league average of 8.2%, so there is certainly still concern there.
As for pitch type, the left-handed reliever relies mainly on a four-seam fastball, sweeper, and changeup. He was also credited with throwing a sinker (6.2% of the time) and cutter (3.6% of the time) in 2023. His best pitches were the two he threw the most often, as the xBA on his four-seamer was .183 and on his sweeper was .156. Both terrific numbers.
Specifically, the horizontal movement he gets on his four-seam fastball was 9.1% higher than the average in the major leagues last season, a figure that only trailed Reds unorthodox starting pitcher Nick Lodolo.
Diekman’s second-best pitch, his sweeper, generated a whiff rate of 37.3%. A figure that ranked in the 76th percentile among pitchers who threw that pitch at least 29 times last season (136 total qualifiers). So, when he needs a swing-and-miss Diekman can rely heavily on that big sweeping offspeed pitch.
Final Thoughts
If Diekman is able to keep that same adjusted delivery he had in Tampa Bay, the Mets should be inline to get an extremely effective left-handed relievers at a cheap rate. Diekman finished as one of the best left-handed relievers in the game last season after making the transition to Tampa Bay. The key for the 37-year-old will be keeping the walk rate down closer to his career average rather than the numbers that plagued him with the White Sox.
With Diekman, the Mets now have a bullpen that profiles pretty well on paper. Fangraphs currently has the Mets’ bullpen ranked No. 12 when it comes to total projected wins above replacement in 2024. Granted, that figure is a tad inflated by Edwin Díaz, but, overall the unit that currently projects to contain Díaz, Adam Ottavino, Brooks Raley, Diekman, Drew Smith, Jorge López, and newest signing Shintaro Fujinami, plus the winner of a fierce camp battle between a plethora of guys, should be a very large upgrade over where it was entering last season and at the offseason’s beginning.
