Spiers had been in the midst of a rehab assignment at Triple-A Louisville while working his way back from a shoulder impingement, but he was pulled off the assignment about a week ago after experiencing soreness in his right biceps. He underwent a couple of MRIs since then, and a second opinion confirmed that Tommy John surgery was necessary. No date has been set for Spiers' procedure, but the surgery will be performed by renowned arm specialist Dr. Keith Meister. In addition to missing the remainder of the season, Spiers will be at risk of missing the entire 2026 campaign as well.

Reds manager Terry Francona confirmed the results of the MRI and said Spiers will seek a second opinion. "It's not cut and dry, but there is some concern," Francona said. Spiers first hurt the shoulder in April and was transferred to 60-day injured list in late May.