Which D-backs Minor League Relievers Can Contribute in 2023?

Looking at relief pitchers on the 40-man roster and potential 2023 call-ups.

© Kirby Lee-USA TODAY Sports

We continue the five-part series on the Diamondbacks bullpen and what can be done to fix it this off-season. Part two will cover the younger relievers, either on the major league roster or in the organization's minor league affiliates. The focus will be on players who are with the D-backs Double-A and Triple-A affiliates.

• Current relievers on MLB roster who can compete for a 2023 role
• Current relievers in minor league system who may contribute
• Starting pitcher conversion to reliever candidates in the system
• External trade targets
• Free agents

Part Two: Current Relievers in Minor League System Who May Contribute

40-Man Roster

This is a look at some of the relievers on the current 40-man roster that haven't quite established themselves like the pitchers mentioned in the first installment on the bullpen.

Luis Frias

Frias falls under the category of a player who has a lot of talent for throwing a baseball, but has trouble consistently landing it in the strike zone. Frias throws upper 90s, touching 100 previously this season, with a fastball that has a vertical movement profile. His main breaking pitch is a spike curveball, although Statcast classifies it as a slider, which can be very effective when paired up with the fastball. He also throws a changeup, which has some swing-and-miss potential against left-handed hitters when he can locate it down in the zone. The potential for a closer is there, but he'll need to start being more aggressive in the strike zone and not lose focus in games.

J.B. Bukauskas

Bukauskas was a big part of the Zack Greinke deal in 2019, but hasn't been able to crack the big leagues this year with various injuries. After an initial trial run with Arizona in 2021, Bukauskas saw his fastball get hammered and got good results with his slider. He has decent numbers with Reno this year posting a 2.41 ERA and a 16/4 strikeout to walk ratio in 19.1 innings with Arizona's Triple-A affiliate. Due to his injury history, the D-backs will need to see if Bukauskas can make the adjustments to succeed in the big leagues instead of wasting his bullets in Reno. His arsenal features a 4-Seam Fastball that has more of a horizontal movement profile, a wipeout slider, and a solid changeup. If he's able to make the adjustment in the big leagues, I see a future setup man in the backend of the pen.

Taylor Widener

Widener is a converted starter who is another case of a pitcher who has left too many hittable fastballs over the plate. His strikeout to walk ratio has improved in a small sample, with a 12/3 ratio in 13.2 innings. The issue is Widener is prone to giving up a lot of loud contact due to the lack of fastball command. His fastball comes at a flatter angle, due to his 6'0" height, which serves as an advantage since most hitters will anticipate a downhill angle on a fastball due to height. Improvement of the fastball command to go with a solid slider and changeup could thrust Widener into a potential setup role.

Sean Poppen

Poppen showed some promise with the D-backs in 2021, but hasn't been able to build on that since 2022. A sinker/slider guy who sits mid 90s and manages to avoid barrel contact, there is some utility as a middle innings reliever who piggybacks off a left-handed starter. The main issue is the lack of swing and miss, with an 18% strikeout rate this season, which limits the amount of situations Poppen can be successfully deployed. Add in that he's going to be out of options in 2022, Poppen may be one of the arms that gets bumped off the 40-man roster this winter.

Tyler Holton

Holton has been an up-and-down arm for the D-backs this season, although his small sample in the big leagues suggests he could contribute in more medium leverage situations. With two options remaining, Holton will likely bounce between Triple-A Reno and Arizona as a depth arm. He sits 90-92 on the fastball that gets hammered when he bites off too much of the strike zone, but has an assortment of secondary pitches that can keep hitters off-balance. Holton has a solid feel for when to change speeds and solid enough command to make it all work. 2023 could determine if he's a fixture in the bullpen or if he's just an up-and-down arm whose value is tied to just that.

Edwin Uceta

Uceta was a waiver claim the previous winter who hasn't quite been able to build any consistent success in the big leagues. The stuff is decent enough for a big league reliever, as he throws a mid-90s sinker, a curveball, and a changeup. The command of the sinker hasn't been great, as he's left the pitch in hittable locations as a result of falling behind hitters. Jumping ahead of hitters and then using his changeup and curveball to put them away will be key in order to establish himself in a big league bullpen. With one more option left, Uceta should still be on the 40-man roster next season.

Keynan Middleton

Middleton is another example of a guy who has the stuff to pitch in a big league bullpen, but leaves his fastball in too many hittable locations. With the fastball being a big component of his arsenal, he'll need to move it out more towards the edges of the strike zone for swings and misses instead of loud contact. Getting ahead of hitters will also be key, which opens up the slider and changeup when Middleton needs to put away hitters. 

Minor Leagues

This section covers potential call-ups for next season.

Mitchell Stumpo

Stumpo is one of many players that will be Rule 5 eligible in the offseason. Stumpo was mentioned as a potential call-up, with a mid 90s fastball and a sharp-breaking slider. Walks have been an issue for Stumpo in Reno, which may be the only reason he isn't getting a look in the big league bullpen, with 31 in 42.1 innings. His upside is likely a right-handed matchup guy in the middle innings that could potentially handle a sixth or seventh inning role.

Justin Martinez

Martinez is a converted starter, who has pitched primarily in relief since returning from Tommy John surgery. He lights up the radar gun, hitting a top speed of 98 with his 4-Seam Fastball. He also utilizes a slider and a changeup as his secondary offerings, with the slider going to right-handed hitters and the changeup for lefties. 

Levi Kelly

The last two years have been unkind for the former eighth round pick, as he's struggled with shoulder injuries and thoracic outlet syndrome. Getting his velocity and stuff back to where it was in 2020 will be key for the D-backs to get him back on track. That version of Kelly threw 95-97 with a wipeout slider that generated whiffs on both sides of the plate. If there is any indication that his stuff and command have returned, it won't be long before Kelly finds himself in the big league bullpen and could be a potential high-leverage arm.

Kyle Backhus

Backhus is an interesting left-handed reliever that has thrust himself into the conversation of a 2023 call-up. He's got the least impressive stuff of the group, but has a similar pitch mix to Joe Mantiply. Backhus could be a potential matchup lefty in the mold of Kyle Nelson that has a slider that's difficult to pick up from a funky arm angle. He'll have a chance to showcase that he's worthy of a 40-man roster spot when he pitches in the Arizona Fall League next month.

Blake Workman

Workman is a pitcher who puts up good strikeout and walk numbers, but has a habit of getting hit hard when he challenges hitters. He commands a mid 90s fastball pretty well to the edges of the strike zone and has a quality curveball that he likes to throw for called strikes and getting chases below the zone. Workman isn't likely to develop into a high-leverage arm, but as a cheap and moveable middle relief arm there is some value.

Justin Lewis

Lewis hasn't had much success in the upper minors with Arizona, but due to his length and 6'7" frame presents some unique angles for opposing hitters. His fastball sits in the mid 90s after filling out and he can throw a downer curve and a changeup down in the zone. He's an arm that might get some looks as a potential Rule 5 candidate from teams thinking that the high run prevention is a result of the environment instead of his actual pitching skill. 

The D-backs front office will need to take a hard look at which players in these two groups are worth holding on to and which players they need to move on from. When it comes to fixing the bullpen, it's critical that they make timely decisions on players that aren't capable of getting big league outs and avoid drawing things out like the past two seasons.