This article is part of a series chronicling the individual seasons of players who appeared for the Arizona Diamondbacks in 2024.

Reviews for players who still have rookie eligibility for 2025 will appear in our prospect season reviews. Players are presented in the reverse order of their aWAR, an average of Baseball Reference and FanGraphs WAR.

2024 Contract status: Arbitration, one year, $925,000.

The Arizona Diamondbacks’ bullpen had its moments of greatness, along with its inconsistency. But left-hander Joe Mantiply put forward one of the more consistent seasons from a D-backs reliever. He might not have put out the flashiest numbers – as he rarely does – but the former All-Star served his role admirably, and as a whole, pitched better than the box score might show.

As relief numbers can be volatile, Mantiply’s season began on a somewhat low note, giving up three hits and two runs against the Colorado Rockies. That set his ERA at a lofty 18.00 after just one appearance.

After that, he put out five scoreless showings, allowing just two hits in that span. He allowed a run in just three of his 14 April appearances, good for a 3.09 monthly ERA.

In May, he collected his first save of the season, and also made his first start of 2024, serving as a one-inning opener against the Los Angeles Dodgers, doing so in scoreless, hitless fashion..

A poor outing against the Tigers in a blowout loss on May 18 saw his ERA spike again, when he gave up three runs without recording an out. But he allowed just three hits and one run in his other 10 May appearances.

He maintained an effective middle relief pace, tending to surrender runs in the middle of months, but pitching well for the most part. He never allowed more than five earned runs in a month’s worth of action, and finished with a 3.92 ERA.

But that number is bolstered by a stellar 2.51 FIP and 3.24 xERA, meaning he was often the victim of poor batted ball luck, and rarely gave up the long ball, with a sparkling 0.15 home runs per nine, with just one homer allowed in 59.2 innings.

Those 59.2 innings nearly matched his 2022 total (60.0), and the former All-Star pitched nearly as well as he did in his 2022 campaign, despite being the only effective left-hander in Arizona’s bullpen for the majority of the season until A.J. Puk was added at the Trade Deadline.

Mantiply had to face some of the game’s best hitters, and wasn’t limited to just left-handed batters. Of course, he found some success against MLB’s top superstar in Shohei Ohtani, limiting the Japanese sensation to just one hit and three strikeouts in nine plate appearances.

Mantiply’s ability to deliver against some of the best of the best, while pitching to an overall excellent season despite some occasionally poor results, made him a valuable asset to the D-backs’ relief corp, maintaining a consistent stability in the heart of close games.

2025 Contract status: Arbitration 2

Mantiply will be arbitration-eligible again in 2025. While he is 34 years old, he’s only pitched significant innings in the majors in his last four seasons. He made $925,000 in his first year of arbitration in 2024, and will be a likely return for the D-backs in 2025.

Spotrac estimates Mantiply’s second year of arbitration will land him a deal worth $1,580,000 in 2025, and he won’t be a free agent until 2027.

With the steady, consistent nature of his play, and the premium that effective left-hand relievers are considered to be, it will be a surprise if Mantiply is not pitching significant innings for Arizona again for the 2025 season, barring injury or severe underperformance.