The Arizona Diamondbacks are officially in scramble mode when it comes to their bullpen — and at this rate, they should start looking outside the organization for reinforcements. What started the 2025 season as an unstable unit is now teetering on the edge as injuries and inconsistent performances pile up.
The latest setbacks include right-hander Justin Martinez, whose recent dip in velocity turned out to be more than just fatigue, was placed on the 15-day injured list with right shoulder inflammation. Meanwhile, A.J. Puk — the newly acquired lefty many expected to join Martinez in sharing the closer role — has landed on the 60-day IL due to elbow inflammation. In response, the Diamondbacks called up left-hander Jose Castillo from Triple-A Reno, but this patchwork solution only doubles down on the glaring lack of bullpen depth.
Arizona's bullpen ERA sits at 4.46, ranking 22nd in Major League Baseball. That’s despite logging the ninth-fewest innings among all bullpens — meaning their workload isn’t unusually high, but the efficiency just isn’t there.
Closer-by-committee won't solve the Diamondbacks' bullpen crisis
To stabilize the late innings, the D-backs have turned to a couple of arms — Kevin Ginkel, who briefly held closing duties last season when Paul Sewald was unavailable, and veteran right-hander Shelby Miller. It's another classic closer-by-committee approach, but it may be time to ask whether that strategy is actually making things worse.
A cautionary tale lies just a season ago with the 2024 Kansas City Royals. That team began the season with no defined closer, relying on matchups, analytics, and intuition. The results were a 4.21 bullpen ERA, ranking 21st. But once they announced Lucas Erceg as the primary closer, the unit responded with a 3.77 ERA the rest of the season, and an elite 2.77 ERA in September, good for 4th-best in baseball. Royals relievers credited that success to defined roles — knowing what’s expected of them and when.
It’s a blueprint Arizona should strongly consider. Shelby Miller is making the case to take over the closer role while Puk and Martinez are out and it’s unbearably loud. Through 13 games in 2025, Miller has tossed 13.2 scoreless innings, allowed just seven hits, struck out 15, and walked only four. He’s 2-0 with a pristine 0.00 ERA and just notched his first save of the season. He’s been absolutely dominant.
Compare that to Ginkel, who is still finding his footing after a brief IL stint. In his first two outings since returning, he’s already surrendered a home run and hasn’t looked entirely sharp. While Ginkel has experience in the closer role, the hot hand belongs to Miller — and the Diamondbacks ride it.
Arizona has to stop juggling roles and start defining them. The Royals learned it the hard way — with the state of their bullpen the Diamondbacks would be wise to skip that phase altogether.