Arizona Diamondbacks left-hander Kyle Backhus (43) pitches against the Cleveland Guardians at Chase Field on Aug. 19, 2025. Joe Rondone/The Republic / USA TODAY NETWORK via Imagn Images

How Diamondbacks Rookie Earned Role in 2025

Originally posted on Arizona Diamondbacks on SI
By Alex D'Agostino | Last updated Dec 5, 2025 10:00 AM ET

It took a massive number of players for the Arizona Diamondbacks to endure the injury-riddled 2025 season.

That roster attrition (and overall underperformance) was most intensely felt in the D-backs' pitching staff — particularly the bullpen.

After left-hander A.J. Puk went down with an injury that would eventually require Tommy John Surgery, Arizona was quite starved for quality left-handed relief.

That unfortunate occurrence did provide an opportunity for rookie left-hander Kyle Backhus, who stepped into a major league role for the first time this season.

As Arizona Diamondbacks On SI continues to walk through the individual seasons of every player who appeared on the field for Arizona in 2025, the below article will be updated with the proper article links as they are published.

Arizona Diamondbacks 2025 Player Review: Kyle Backhus

Alex D'Agostino

Backhus began 2025 with the Triple-A Reno Aces with a successful start. On June 8, he was called up to the major leagues for the first time.

Backhus was immediately effective at the major league level, allowing just one earned run over his first eight appearances. His unique, nearly-sidewinding delivery was able to baffle major league hitters, and he looked immediately prepared for the brightest lights.

He went through a rough July, but then pitched to a 3.18 ERA over 11.1 innings in the month of August. Unfortunately, he struggled to get outs in a high-leverage role (out of necessity) in September, and was eventually sent back to Triple-A.

He was very effective at the minor league level in 2025, throwing to a 2.05 ERA in 26.1 innings with the Aces despite the hitter-friendly environment. It was clear he had made the jump beyond Triple-A level, and showcased success in MLB.

Kyle Backhus: 2026 Outlook

Backhus' early success (even despite the late struggles) should earn him an opportunity to contribute at the major league level in 2025.

But in order to be a reliable contributor, he'll need to improve his splits. Backhus dominated left-handed batters, allowing three runs and striking out 10 in 11 innings. But against righties, he gave up 11 runs (10 earned) over 14 innings.

Backhus has the stuff, delivery and major league mentality needed to be an impact reliever, even if his stuff stays in the low 90s.

There is potential present, and his MLB debut season was certainly impressive, but he'll need to find a way to round out his game to earn more innings for Arizona.