Keller underwent right elbow UCL reconstruction with internal brace and flexor tendon repair surgery Tuesday, Lochlahn March of The Philadelphia Inquirer reports.
Right after the All-Star break, Keller was diagnosed with a torn UCL in his right elbow. He's expected to pitch 13-to-16 months from Tuesday's surgery, so the earliest that he could return to action would be late in the 2027 season, though it's more likely that he'll be aiming toward being fully healthy for the start of the 2028 campaign. Keller will finish the 2026 regular season with a 4.02 ERA, 1.34 WHIP, 13 holds, three saves and a 32:13 L:BB across 31.1 innings.