2024 Diamondbacks Camp Battles: 2nd Left-Handed Reliever

The second camp battle that could affect the makeup of the Diamondbacks Opening Day roster that we're highlighting at Inside the Diamondbacks is the second left-handed reliever. With Arizona carrying eight relievers to begin the season, the likely bullpen will carry six right-handers and two left-handers. There may be points in the year where they carry as many as three lefties.

Joe Mantiply, who will turn 33 one day before the season starts, is the lone roster lock from the group of left-handers. Despite a 4.62 ERA in an injury-riddled season, Mantiply's underlying metrics suggest a still useful arm. Behind him are a string of left-handed arms that all have a chance to make the roster for one reason or another.

With the left-handers they're entering spring with, the top four candidates all have at least two options remaining. That gives them a decent amount of depth, as the bullpen will have constantly moving parts throughout the season. 

Andrew Saalfrank

2023 Stats: 10 G, 10 1/3 IP, 0.00 ERA/3.45 xERA, 14.6% SO, 9.8% BB; 2024 Projection

Saalfrank is the leading candidate to make the roster due to his strong performance to close out the regular season. He has 10 regular season and 11 postseason games under his belt with a good combination of chases, whiffs, and ground ball rate projecting well for a longer stint. He had a brief hiccup when dealing with some of the left-handed power bats in the Phillies lineup in the NLCS.

The case for Saalfrank is one of potential, as he could become the team's best left-handed reliever. At the current stage of his career, he's not a back of the bullpen arm, but there's potential for him to grow into one. We saw that with Kevin Ginkel last year, who went from an up-and-down arm to arguably their best reliever. Despite a short track record, he's been put in stressful situations in both the regular and postseason with mostly positive results. 

The case against Saalfrank isn't particularly strong, because he has many potential run prevention skills. Despite only 21 MLB games, he's been battle-tested and has earned more opportunities.

Kyle Nelson

2023 Stats: 68 G, 56 IP, 4.18 ERA/3.63 xERA, 28.0% SO, 5.9% BB; 2024 Projection

Nelson could find himself on the outside looking in for a roster spot if the team only carries two left-handers in his bullpen. In terms of strikeout and walk rate, he is well above the average reliever but his overall results were very middling. That was due to a 1.9 home runs per nine innings, as batters that make contact have hit him hard. That's something he'll have to figure out. He has two options remaining, so if he doesn't make the team he'll be one of the first relievers they'll bring up from Reno when an injury or performance warrants it.

The case for Nelson is he is a more established arm than the other competitors with significantly better strikeout and walk rates. He is exceptional at inducing chases and whiffs with his plus-plus slider. That's allowed him to be an effective reliever despite a 91-94 MPH fastball that lacks any notable characteristics. The strikeout and walk rates create a strong foundation for success, but he needs to improve his in-zone command to limit the loud contact.

The case against Nelson is his batted ball profile is significantly weaker compared to Saalfrank, despite the latter's short track record. He has significantly below average marks in various contact metrics on Statcast, as the expected wOBA on contact (xwOBACON) was .393. With only one run prevention skill and completely dependent on chases to miss bats, it's a bit worrisome when he doesn't have his best stuff. If he can improve his ability to limit loud contact, he's got a chance to develop into a quality left-handed reliever.

Brandon Hughes

2023 Stats: 17 G, 13 2/3 IP, 7.24 ERA/5.34 xERA, 27.0% SO, 12.7% BB

Hughes had emerged as a bullpen arm for the Chicago Cubs in 2022, but was not able to repeat that success in 2023. He was troubled by knee issues, which ultimately led to knee surgery that ended his season in June and eventually non-tendered in November. While he's not likely to wind up with a roster spot on Opening Day, he has a chance to potentially have an impact on the season as the team will need 15-20 relievers to get through a season.

Even in the injury-plagued year, the same skills that made him effective in 2022 were still there. There's a bit more velocity in his fastball compared to Nelson, averaging 93.3 MPH, and he also utilizes a two-seamer that can work to both sides of the plate. If healthy, he's a capable left-hander in a major league bullpen.

The case against Hughes is simply there are more established options ahead of him right now. In order to get him on the active roster, the team would need to clear out a 40-man roster space for him. However he also has three remaining options on his contract, so stashing him in the minors would not be difficult either.

Likely Winner

With the premise that Mantiply is a roster lock, then Saalfrank is the likely winner of these three pitchers. He has the minor league track record of missing bats and managed to avoid loud contact in his first MLB trial run. That was the main difference over a more established arm like Nelson, who actually has fairly good peripherals on the mound otherwise.