D-backs Reliever's Major League Return Was an Unfortunate Letdown

The Arizona Diamondbacks' former bullpen contributor just hasn't been the same since his injury.

Arizona Diamondbacks pitcher Kyle Nelson throws to the San Francisco Giants in the third inning during a spring training game at Salt River Fields on March 5, 2025, in Scottsdale. | Rob Schumacher/The Republic / USA TODAY NETWORK via Imagn Images

The Arizona Diamondbacks did not have the luxury of being picky about who manned their severely battered and underperforming bullpen in the 2025 season.

It took numerous arms — some familiar faces and some new journeymen — to fill out a year plagued by injuries for the D-backs. While some enjoyed varying levels of success, many of their emergency relief options' seasons were short and ineffective.

One such short and ineffective tenure was that of left-hander Kyle Nelson — a veteran of the D-backs' organization.

While Nelson has been, at times, a legitimate contributor to Arizona's bullpen, it had been some time since he'd seen major league action, and he was a shell of himself in 2025.

As Arizona Diamondbacks On SI continues to break down the individual seasons of every member of the 2025 D-backs roster, the below article will updated live. Check out the below link:

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Nelson had been a regular member of Arizona's bullpen, with solid, albeit not flashy results in 2022 and 2023. But he only pitched 10.2 innings in 2024 before going down with a shoulder injury.

As it turned out, Nelson needed Thoracic Outlet Surgery — a brutal procedure that can significantly impact one's career and ability to pitch.

Unfortunately for Nelson, that impact was felt strongly. Upon his eventual return, he was knocked around for a 9.09 ERA over 33.2 innings in Triple-A Reno. Even in the hitter-friendly environment of the PCL, his results were very poor.

Nelson was designated for assignment on July 2, but cleared waivers and returned to Reno.

The D-backs would eventually call him up on August 1, and he made his first appearance since April of 2024 that day.

One game later, Nelson recorded his first ever major league save, gritting out a tough ninth inning against the Athletics in Sacramento.

But on August 5, Nelson walked the bases loaded without recording an out against the Padres. The command clearly was still not there, and he returned to Reno.

2026 Outlook: Kyle Nelson

According to his transaction log, Nelson has elected free agency. He may be a re-signing for minor league depth, and it's not impossible to imagine him pitching better than he did in 2025 coming off a brutal surgery.

But it's unlikely he'll be throwing quality innings for Arizona's major league club anytime soon. The days of a 2.19 ERA in 2022 are long past.