Diamondbacks' Zac Gallen Dealing With Surprise Elbow Injury

This is surprising news.

May 12, 2026; Arlington, Texas, USA; Arizona Diamondbacks pitcher Zac Gallen (23) waits in the dugout during the first inning against the Texas Rangers at Globe Life Field. Mandatory Credit: Andrew Dieb-Imagn Images | IMAGN IMAGES via Reuters Connect

Arizona Diamondbacks struggling right-hander Zac Gallen has been sent back to Arizona, and is dealing with a surprise injury, according to multiple new reports.

Gallen received imaging, and is likely to land on the injured list with elbow inflammation. Left-handed rookie Mitch Bratt is on the D-backs' taxi squad, and will most likely take Gallen's place in the rotation for Sunday's game against the Los Angeles Dodgers.

Zac Gallen is dealing with right elbow inflammation. He will not start tomorrow and is likely headed to the injured list. Mitch Bratt is likely to start in his place.

— Nick Piecoro (@nickpiecoro) July 11, 2026

Diamondbacks' Zac Gallen dealing with elbow inflammation

It's simply been a brutal season to this point for Gallen, who returned to the D-backs on a one-year deal following a career-worst 2025 season.

Despite hopes of a bounce-back season, things have gone from bad to worse for Arizona's former ace. He has a 6.34 ERA over the course of 19 starts (98 innings), which ranks last among all qualified major league starters. His 9.00 first-inning ERA is the second-worst in baseball.

Arizona Diamondbacks right-hander Zac Gallen (23) talks with catcher Adrian Del Castillo (25) and pitching coach Brian Kaplan after giving up two home runs in the 5th inning against the San Francisco Giants at Chase Field in Phoenix, on July 1, 2026. | USA TODAY Network via Reuters Connect

Gallen is striking out the fewest batters of his career, with a 5.60 K/9 and 13.9% strikeout rate. He's not walking an inordinate number of batters, but he's also not picking up much swing-and-miss, and his stuff has been hammered when located in favorable hitting positions. He's giving up 1.65 home runs per nine innings, which is also a career-worst figure.

But despite his recent struggles on the mound, the one thing Gallen has been is durable.

The right-hander has been a workhorse  — regardless of result — for the near-entirety of his Diamondbacks career. He missed a month of 2024 with a hamstring injury, but has not had to deal with many physical ailments since a bumpy 2021 season. He has thrown 180-plus innings in three of his four seasons prior to 2026.

The Diamondbacks' rotation, meanwhile, has already dealt with its fair share of injuries in the 2026 campaign. Michael Soroka (glute strain) and Ryne Nelson (elbow strain) are both on the IL, which has necessitated fill-in efforts by rookies Jose Cabrera and Bratt, as well as a successful return to the rotation for Brandon Pfaadt.

There is little pitching depth remaining for Arizona. Corbin Burnes, who had a setback in his rehab process, will not be back by the All-Star Break as anticipated. Soroka might not return as quickly as expected, either. The depth options in the minor leagues are limited to Bratt, lefty Kohl Drake and a handful of other Triple-A arms with less-than-inspiring numbers.

As of now, it is unclear if Gallen is destined for a lengthy IL stint, or if this is the type of elbow injury that would require surgery. Diamondbacks On SI will continue to report on Gallen's status moving forward.