Can Justin Martinez Stabilize the Diamondbacks Bullpen?

The Arizona Diamondbacks are about to receive a boost to their tired and ineffective bullpen. Closer Justin Martinez appears to have just successfully completed his rehab from an injured list stint, and should be rejoining the team for the weekend series starting Friday against the Cardinals in St. Louis.

Without Martinez, or co-closer A.J. Puk, the D-backs bullpen has been a disaster. Shelby Miller has filled in as the closer since Martinez went on the injured list with shoulder inflammation on May 1.

Miller has had his good moments and bad since that date, recording five saves and blowing two while posting a 5.64 ERA. He's had to work in nine of the team's 19 games this month, including each of the last three. He's clearly been overworked, but has taken the ball whenever asked. Without him, the D-backs would have been in far worse shape.

Meanwhile most of the other pitchers the team was depending on to pick up the slack have been inconsistent and generally quite poor. Kevin Ginkel (8.31 ERA), Ryan Thompson (15.19 ERA), Jalen Beeks (6.14 ERA) and Juan Morrillo (6.75 ERA) have combined to throw 29.1 inning and allow 28 earned runs in May, (8.59 ERA).

Add to that the struggles of Joe Mantiply, who was optioned back to Triple-A Reno after two more disastrous outings, and Jose Castillo, who was so bad he was DFA'd and got traded to the Mets, and it has been as bad as one could possibly imagine.

And yet somehow the D-backs are 26-23, just 2.5 games out of a Wild Card spot, and four games behind the NL West leading Dodgers heading into Wednesday night's series finale. They are 10-9 in May. There have no doubt been several games that definitely felt like they should have won were it not for bullpen meltdowns, leading to missed opportunity to post a better record.

One statistic that will probably surprise most people, however, is that the Diamondbacks are 8-8 in one run games. That's exactly league average. Even the Dodgers are just 8-7 in such contests, and the Giants are 10-8. Meanwhile their upcoming opponent, the Cardinals, who have a better overall record at 27-22, are 7-8 in one run games. Also notable is that the D-backs have 14 blown leads, but 12 comeback wins.

With Martinez's return, he should slide right back into a high leverage role, and presumably retake the closer's role very quickly. That should allow Miller, Ginkel, Beeks, and Thompson to move back into more established set up roles.

If Martinez is effective, the stabilization of the bullpen could happen quickly. But it's no forgone conclusion that just because Martinez is back he will be effective. All of his medical imaging and exams check out clean. There was no injury to Martinez. Yet he suffered a dead arm phase, and saw precipitous velocity drop in several outings just before going on the injured list.

Perhaps the issues were mental, as has been speculated on by many. Whether physical or mental, it's critical to the Diamondbacks chances to make the postseason that Martinez resume being the dominant pitcher he is capable of.

In 2024 Martinez threw 72.2 innings and posted a 2.48 ERA while striking out 91 batters. 19 times he was handed leads in what were classified as save situations. He record eight saves, nine holds, and blew the lead twice. That 17 for 19 conversion rate of 89.5% was well above average. In 2025 he's recorded three saves and three holds in seven save situations, 86%.

It's a lot to ask, and truly unfair to expect Martinez to be the catalyst that turns the bullpen into an effective unit all on his own. But he is a crucial piece of the puzzle, without which nothing has seemed to fit.

A.J. Puk meanwhile has begun his throwing program this week, throwing out to 60 feet. He was previously moved to the 60-day IL with a flexor tendon strain and is not eligible to be activated before June 18.

Beeks is the lone lefty in the bullpen and has been overworked, throwing 24 innings so far, or a pace for 79. The team does not appear to feel confident in any of their internal options from the left side, as when they optioned Mantiply they called up right-hand pitcher Scott McGough. It would not be a surprise to see the team attempt to add left-handed relief help from outside the organization in the near future.