Santillan will undergo surgery Thursday to repair a left hip labral tear, Gordon Wittenmyer of The Cincinnati Enquirer reports.
Santillan attemped to pitch through the injury the last couple weeks before officially shutting things down Tuesday. The Reds expect to have a better idea as to Santillan's rehab timeline following the procedure. He finished with a 6.42 ERA and 36:28 K:BB over 40.2 innings in 2026.