If they only had a decent bullpen, the Diamondbacks would have made the playoffs.

If I had a dollar for every time I have seen or heard a Diamondbacks fan say those very words, I might have been able to beat Mat Ishbia’s offer to become the next owner of the Phoenix Suns.

The claim is understandable. Diamondbacks relievers took a league-leading 41 losses in 2023. The average big-league bullpen lost 28 games. That’s a difference of 13 games — the exact number of games by which the Diamondbacks trailed the Philadelphia Phillies in the National League wild card race.

But pitcher losses are a fickle stat for a number of reasons that I won’t detail now. Based on win probability added (WPA), a more reasonable estimate for the number of games lost due to the bullpen is around eight or nine at most. Nonetheless, the D-backs will have to make improvements in that regard to have any shot at the postseason in 2023.

Whether the D-backs did enough to bolster the ‘pen this offseason is a question that only time can answer. For now, let’s take a look at what they do have, organized by likelihood of making the Opening Day roster.

Diamondbacks reliever Joe Mantiply pitches against the American League during the sixth inning of the 2022 MLB All-Star Game at Dodger Stadium.
Diamondbacks reliever Joe Mantiply pitches against the American League during the sixth inning of the 2022 MLB All-Star Game at Dodger Stadium. (Jayne Kamin-Oncea/USA TODAY Sports)

The shoo-ins

RHP Miguel Castro, LHP Joe Mantiply, RHP Scott McGough

As the headline suggests, there’s not much to talk about here. Suffice it to say that the team didn’t sign Miguel Castro to a one-year contract, $3.5 million contract with a team option for 2024 just to have him pitch in the minors. Castro threw postseason innings last year for the New York Yankees and, with an upper-90s sinker and a wipeout slider, is all but certain to make the Opening Day roster.

Roughly two weeks after signing Castro, the D-backs also signed right-handed reliever Scott McGough to a two-year contract with a mutual option for 2025. McGough bounced around a few major-league organizations for several years before taking his talents to Japan in 2019. He went on to pitch in the NPB for four seasons, most recently tallying a 2.35 ERA, 0.97 WHIP and 59 strikeouts in 53.2 innings in 2022. With 69 total saves over the past two seasons, McGough has more recent closing experience than anyone on this list. It is not unreasonable to think he could close some games for the D-backs in 2023.

Lastly, Joe Mantiply was the D-backs’ lone All-Star representative last year and will almost certainly return as the team’s primary weapon against left-handed hitters. Mantiply’s 3.86 ERA and 1.29 WHIP after the All-Star break were not on par with his first-half numbers, but his second half was hardly a meltdown. Expect to see Mantiply play a big role in the bullpen in 2023.

Diamondbacks reliever Mark Melancon throws against the San Francisco Giants at Oracle Park.
Diamondbacks reliever Mark Melancon throws against the San Francisco Giants at Oracle Park. (Robert Edwards/USA TODAY Sports)

The very-good-chance club

RHP Kevin Ginkel, RHP Mark Melancon, LHP Kyle Nelson

Entering last season, the Diamondbacks’ bullpen picture looked relatively stable in no small part because of Mark Melancon. After leading the league in saves with the San Diego Padres in 2021, Melancon was arguably a tier above any other closer that D-backs general manager Mike Hazen has acquired in his tenure. Nonetheless, the 37-year-old was unable to keep the closer role for the whole season, and he ultimately took 10 losses, twice as many as in any other season of his 14-year career.

In 2023, Melancon no longer projects as the surefire closer of the D-backs. Still, 2022 was not the only down-year of his career, and the possibility of a bounce-back likely gives him an inside track at a roster spot. Melancon is set to make $6 million in 2023 and has a $5 million mutual option for 2024 with a $2 million buyout.

On the other side of the spectrum is 26-year-old left-hander Kyle Nelson, who pitched to a 1.57 ERA for the D-backs through early August before hitting the injured list with back spasms. Nelson returned in early September but struggled with command, walking six in 2.2 innings. He finished the year back on the IL with left elbow inflammation.

Nelson’s 2.19 ERA for the year was undeniably helped by an unsustainably low home-run rate (he allowed only one all year) and a relatively low BABIP of .243. Nonetheless, Nelson was one of the team’s most reliable relievers in 2022, and he figures to be a strong candidate to make the team if healthy.

The most intriguing name in this group is probably Kevin Ginkel. After down years in 2020 and 2021, the 27-year-old looked like a different pitcher after being called up on Aug. 1 of last year. In 29.1 innings, Ginkel logged a 3.38 ERA, 1.30 WHIP and a solid strikeout rate of 24.2 percent. Notably, Ginkel’s fastball velocity ticked up to a career-high 96.2 MPH and his slider got hitters to chase more than ever.

As with Nelson, it should be noted that Ginkel allowed only one homer in the majors. That level of home run prevention is unsustainable, but Ginkel’s strikeout rate was promising and his fastball-slider combo looked like backend reliever material. Ginkel is not only a strong candidate for a roster spot, but a dark-house candidate to close some games in 2023.

Diamondbacks reliever Justin Martinez pitches in the Arizona Fall League at Chase Field.
Diamondbacks reliever Justin Martinez pitches in the Arizona Fall League at Chase Field. (Alex Gould/USA Today Network)

The right-on-the-brink club

LHP Tyler Holton, RHP Justin Martinez, RHP Carlos Vargas

Tyler Holton has never been a big-name prospect in the Diamondbacks organization, but the 26-year-old more than held his own in 10 appearances last year, tallying a 3.00 ERA, 1.11 WHIP and six strikeouts in nine innings. The fact that Holton is a lefty works in his favor. As of now, he, Nelson and Mantiply are the only left-handed relievers slated for a spot in big-league camp. Should either Nelson or Mantiply not make the roster, Holton figures to be next in line.

A flame-throwing right-hander, Justin Martinez turned heads in the Arizona Fall League with 13 strikeouts and just three hits allowed over 7.2 innings. At 21 years old, Martinez might be the most promising young reliever in the Diamondbacks’ system, and Hazen said earlier in the offseason that he expects Martinez to come into camp “looking to make an impression.”

Not many pitchers throw as hard as Martinez, but Carlos Vargas is one of the few in the organization. Acquired via trade from the Cleveland Guardians earlier in the offseason, Vargas can touch triple digits with his heater and has a slider in the low 90s. The 23-year-old has yet to pitch in the majors, but he did throw 10 innings in Triple-A Columbus last year and could conceivably be in the mix for a roster spot with a strong spring.

Newly signed Diamondbacks reliever Jeurys Familia pitches for the Boston Red Sox at Fenway Park.
Newly signed Diamondbacks reliever Jeurys Familia pitches for the Boston Red Sox at Fenway Park. (Gregory Fisher/USA TODAY Sports)

The this-guy-is-interesting club

RHP Jeurys Familia, RHP Luis Frías, RHP Jandel Gustave, RHP Mitchell Stumpo, RHP Cole Sulser

It was not long ago that Luis Frías was viewed as one of the best pitching prospects in the organization, but the 24-year-old has struggled mightily with command in limited chances in the big leagues. Over 20.1 career innings, Frías has 22 walks and an ERA of 9.30. Nonetheless, his fastball-curveball combo still looks nasty at times, and it’s too soon to count him out entirely.

As far as non-roster invitees are concerned, the most recognizable name of the bunch is probably Jeurys Familia, who was one of the best closers in the game in the mid-2010s and had a sub-4.00 ERA in the majors as recently as 2021. The 33-year-old struggled to the tune of 6.09 ERA in 2022, but his veteran presence could prove valuable in what projects as a relatively inexperienced D-backs bullpen.

The team also signed right-hander Jandel Gustave to a minor-league deal with an invite to camp. Gustave has the best recent big-league numbers of any non-roster invitee, with a respectable 3.86 ERA, 1.29 WHIP and 27 strikeouts in 28 innings with the Milwaukee Brewers in 2022. Gustave primarily throws a mid-90s sinker and a mid-80s slider.

Another interesting name to keep an eye on is Mitchell Stumpo, who seemed poised to crack the majors at some point last year after working his way up from Low-A Visalia to Triple-A Reno in 2021. Stumpo never got that chance, likely because of an inflated 16.6 percent walk rate with the Reno Aces last year. Nonetheless, the 26-year-old still generates plenty of swing-and-miss and could conceivably be a strong spring away from making the Opening Day roster.

Finally, the D-backs claimed 32-year-old right-hander Cole Sulser off waivers from the Miami Marlins back in November. Sulser had been expected to be a big part of the Marlins’ bullpen after coming over in a trade with the Baltimore Orioles last April. Ultimately, his stuff took a step back, and he managed only a 5.29 ERA in 34 innings. In 2021 with the Orioles, he was one of baseball’s best relievers, tallying a 2.70 ERA and 73 strikeouts over 63.1 innings.

The story of Sulser’s last two years is a microcosm of what happens to relievers all the time. In a one-year span, any reliever can go from one of baseball’s best to one of its worst. It is no mistake that relievers are widely viewed as the game’s most volatile assets.

In 2023, the Diamondbacks will hope for a kernel of good fortune after the unmitigated bullpen disaster that was 2022. Unlike last year, the D-backs didn’t acquire any big names this winter, but they arguably did accomplish their goal of improving the level of raw stuff available to them. Perhaps, that will be enough to reverse a longstanding trend of bullpen woes.

It bears mentioning that the team could look to use one of its young starting pitchers — Ryne Nelson, Drey Jameson, Tommy Henry or Brandon Pfaadt, for instance — out of the bullpen. When asked about the possibility, Hazen was hesitant.

“My biggest concern with moving especially a young pitcher to a bullpen role at the beginning of the season is I feel like you’re making a decision on a pitcher’s season,” Hazen said. “Which is fine. We may make that decision. I’m not ruling it out, but if you do, there’s really no going back in the other direction or you’re increasing the risk of injury to the player.”

Hazen said it is “more realistic” that the team would look to move a starter to the bullpen after Opening Day, and only if the rotation is healthy enough to justify it. As D-backs fans have seen in recent years — particularly in 2021 — that is a big “if.”


Born and raised in Phoenix metro, Jesse’s sports broadcasting career began at the age of 12 when he impersonated D-backs radio voice Greg Schulte on FOX Sports Arizona as the Arizona Diamondbacks Kidkaster. He started writing and podcasting about the Diamondbacks shortly thereafter, and has been doing it ever since. Now, Jesse is a podcast host and writer for PHNX Diamondbacks. Jesse has a math degree and a journalism minor from Azusa Pacific University in Southern California.