Rebuilding the D-backs' Bullpen After the Loss of Shelby Miller

The Diamondbacks’ bullpen took another huge hit Monday night. Right-hander Shelby Miller was placed on the 15-day injured list with a forearm strain.

After the game, manager Torey Lovullo revealed postgame what the plan was for Miller. Talking to reporter Jody Jackson, Lovullo said that his de facto closer will undergo imaging, and his concern level is “not low”.

Parsing through those comments, Lovullo used the phrase high when he mentioned Justin Martinez’s elbow injury last month. Martinez underwent elbow surgery with an internal brace. If we compare Miller’s situation, there could be a huge variance in potential outcomes.

Until the imaging comes back, it’s difficult to assume not only if, but when he’ll return. Miller had been the team’s best high-leverage reliever, with 16 shutdowns and 5 meltdowns. He had a sub-2.00 ERA, even with a 3.11 xERA and 3.20 FIP. With him out of the picture, there’s little certainty left with this bullpen.

With that in mind, it’s time to build a makeshift bullpen until GM Mike Hazen can land the appropriate reinforcements.

Kevin Ginkel is the Closer

Ginkel is now the team’s most experienced late-inning bullpen arm. He has closed games before, but not in a full-time role. He had a chance to fill in last season, although he only converted five of seven opportunities before Paul Sewald returned from an oblique injury.

In the D-backs’ 6-3 win over San Diego, Ginkel was tasked with getting the top of the Padres’ order out. Of course, that meant facing a pair of righties in Fernando Tatis Jr. and Manny Machado. After the game, Lovullo hinted at the possibility of using matchups for the ninth, an approach I consider absurd when considering the current makeup of this bullpen.

The question is whether Ginkel should face lefties in the ninth inning. In 2025, he’s holding lefties to a .219/.325/.438 slash with 14 strikeouts and four walks in 40 plate appearances.

It’s a small sample size, but if you look at his career arc as a back-end arm, he’s done well against lefties. Since 2023, lefties are slashing .222/.294/.364. Those numbers have been trending negatively in each season, as he’s gotten more exposure. However, considering his track record, I think it would be better to ride or die with Ginkel despite his 9.00 ERA.

I may do a deeper dive on Kevin Ginkel and why his numbers have been so bad in a separate entry.

Juan Morillo and Kyle Backhus Get More Higher Leverage Situations

Giving two rookies higher leverage situations and later innings normally is a recipe for disaster. But this team doesn’t have that luxury to make safe decisions without hurting their chances. The current bullpen lacks a good enough track record to ease in those two arms.

It would be better to test Morillo and Backhus, the two most promising arms to come up through the arm system. Morillo will see the bulk of the setup opportunities against right-handed hitters while Backhus and Beeks handle the left-handers.

Morillo doesn’t necessarily have good numbers against right-handed hitters this season, who are hitting .308 with an .868 OPS. But that’s more of a small sample size problem than a bad matchup. With a fastball that’s 98-101 MPH and his best secondary pitch a slider, he matches up well on paper. It’s just a matter of execution.

Backhus, in his short career, has been deadly to left-handed hitters. He’s holding them to a .059 (1-for-17) with no extra-base hits and six strikeouts in 19 PA. His pitch mix of a sinker and sweeper matches up well. However, he’ll need to improve location against right-handed hitters to avoid a repeat of what happened against San Diego, in which he surrendered two hits and a homer.

Yes, that approach can and will lead to losses. It almost cost the D-backs a win Monday night. Backhus and Morillo allowed four baserunners in the eighth inning, putting the potential tying run on base. At the same time, Morillo got two big outs with the bases loaded to effectively end the Padres’ hopes of winning (their win expectancy went from 22.6% to 2.9% on FanGraphs).

With the current placement in the standings, the team has to consider 2026 in their decision-making. There are a lot of roles to fill in next year’s bullpen, with Morillo and Backhus certainly looking like a part of that unit.

The saying goes, “One cannot make an omelette without cracking some eggs.” Backhus’ scouting reports from the minors have one common theme: he’s fearless. In the case of Juan Morillo, success in big situations will be the confidence boost he needs to become a back-of-the-bullpen arm.

Projected Bullpen

Closer: Kevin Ginkel

Primary Setup Relievers: Jalen Beeks, Juan Morillo, Kyle Backhus

Middle/Long Relief/Low Leverage: John Curtiss, Bryce Jarvis, Anthony DeSclafani, Jake Woodford

FanGraphs Depth Chart Rest of Season Projection

• RHP Kevin Ginkel: 27 G, 27 IP, 6 SV, 3.50 ERA, 25.1 K%, 8.3 BB%
• LHP Jalen Beeks: 25 G, 25 IP, 1 SV, 3.72 ERA, 21.5 K%, 8.9 BB%
• RHP Juan Morillo: 25 G, 25 IP, 1 SV, 4.34 ERA, 20.4 K%, 12.6 BB%
• LHP Kyle Backhus: 27 G, 27 IP, 1 SV, 3.99 ERA, 21.4 K%, 9.9 BB%
• RHP John Curtiss: 26 G, 26 IP, 1 SV, 4.41 ERA, 17.7 K%, 7.3 BB%
• RHP Bryce Jarvis: 23 G (2 GS), 34 IP, 4.50 ERA, 18.2 K%, 10.6 BB%
• RHP Anthony DeSclafani: 20 G (2 GS), 29 IP, 4.34 ERA, 19.5 K%, 6.1 BB%
• RHP Jake Woodford: 22 G, 22 IP, 4.69 ERA, 17.4 K%, 6.7 BB%

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D-backs Under Review is Michael McDermott’s publication for deep analysis dives, game coverage, prospect coverage, and breaking down the biggest news topics involving the Arizona Diamondbacks. Michael has been writing about the D-backs since the 2015 season, with stops at AZ Snake Pit, Diamondbacks On SI, Venom Strikes, and Burn City Sports. He has covered over 40 MLB games at Chase Field and the Arizona Fall League.