Diamondbacks 2024 Player Projections: Joe Mantiply

The left-handed reliever has a solid season projected for him

This article is part of a series taking a look into individual Diamondbacks player projections as we head into the 2024 spring training. The projections presented are a composite of the rate (percentage) stats from Steamer and ZiPS as published on FanGraphs. The playing time projection is our own and is based on the current roster as of the time of this writing. Further roster changes will impact the playing time and thus the WAR projection, but not the rate or percentage statistics presented.

Left-hander Joe Mantiply spent the first portion of his 2023 season on the injured list. Arizona's sole 2022 all-star didn't make an appearance until late April, and although he sported a 2.35 ERA through the beginning of May, he would ultimately end up on the IL again through the beginning of July. 

He struggled in his minor league rehab assignments, and looked quite rough in the months following his reinstatement to the majors, but eventually settled into an excellent September, and was featured as the starter for multiple bullpen games when the D-backs needed a bridge in their struggling starter rotation.

Mantiply finished with less than stellar numbers, but was generally dealing with some level of injury, or a slow return therefrom. He pitched nearly half of his 2022 all-star season innings, and was generally removed from higher leverage innings despite being one of Arizona's most clutch arms the prior season. 

The Projection

Joe Mantiply 2024 projection / Alex D'Agostino

Mantiply's projections expect him to look more solid than his struggles in 2023. He's projected a sub-4.00 ERA and a significantly improved strikeout rate. Our usage projections have him seeing relatively limited innings, but still being an effective arm in the middle of the bullpen.

Both Steamer and ZiPS expect a nearly identical ERA. ZiPS' 3.91 projection would be their 5th-lowest expected ERA on the Diamondbacks in 2024. Neither system expects an incredible amount of strikeouts, but still an improvement over his huge dip in 2023. Although Mantiply hasn't allowed 1.0 or more home runs per nine since 2019, the projections expect a slight deterioration in preventing the long ball. 

His aWAR remains consistent, but they predict the southpaw to have a higher FIP (Fielding Independent Pitching) than ERA for the first time in his major league career. Overall, both systems expect a solid season in a milder relief role.

Why Mantiply might outperform this projection

Mantiply is, by all accounts, a much better pitcher than his 2023 numbers might suggest. He spent most of his season dealing with an injury, and has never once pitched to a worse FIP than ERA. Even with his 4.62 ERA in 2023, his 3.84 FIP was that of a very respectable arm. There's no reason to expect that he'd be a worse pitcher than his defense allows him to be in 2024, even with the exceptional defense that is generally played by the Diamondbacks.

His Statcast metrics have at least had bright spots every year of his career. In 2022, he sported an MLB-best 2.5% walk rate, as well as a 99th percentile chase rate, 94th percentile barrel rate, 93rd percentile ground ball rate, and at least above average grades in every other metric besides fastball velocity.

He didn't get much chance to pitch in 2023, but his metrics didn't suffer too much of a drop, despite looking like a down year. His lone deterioration in 2023 came from a worse strikeout rate and a difficulty in making batters miss. However, those haven't been areas where he's struggled for most of his career.

Mantiply is primed for a bounce back, especially with the benefit of less usage and full health. His numbers in 2023 were much inflated by a small handful of rough outings, rather than a pattern of poor performances.

There's little reason to assume that Mantiply won't pitch well again in 2024. While he might not look like his all-star self, he could easily outperform a 3.91 ERA and start to strike guys out at a rate closer to his 2022 season, especially considering his breaking and off-speed pitches sport positive run values.

Why Mantiply might underperform this projection

Mantiply did not pitch like his old self in 2023. His fastball was the biggest red flag, as it showed out at a -5 run value, and was in the bottom 10% of the league in velocity. While velocity isn't everything, Mantiply was barely able to reach 90MPH on both his sinker and four-seamer, and while his secondary pitches generally steal the show, it's hard to dominate in meaningful innings without at least a respectable fastball.

He wasn't given many opportunities to pitch in high leverage, but when he did, he struggled. The left-hander gave up a .350/.366/.650 slash with men in scoring position last season. Part of this could have been due to his injury recovery process, and the advent of the three-headed monster in the 7/8/9th innings, but Mantiply won't be able to be his All-Star self in a mop-up role.

2023 was the worst statistical season where the left-hander saw significant innings. At 33, there could start to be more patterns of regression, and the left-hander could be relegated to a more middle-inning, clean-up role.

Summary

Mantiply is projected a solid season. Although not expected to be a workhorse reliever, he's expected to see an improvement in ERA and strikeout rate, but a worse FIP and walk rate. While it's possible regression could continue, and his stuff doesn't come off as electric, the southpaw has shown himself to be a better pitcher than his numbers show, and the underlying metrics are still solid.

Joe Mantiply Had an Uneven 2023 Season, but Finished Strong