Houston announced McCullers had the ulnar collateral ligament in his right elbow repaired Tuesday.
The 25-year-old was 10-6 with a 3.86 ERA in 22 starts and three relief appearances this year, striking out 142 in 128 1/3 innings. He was 10-4 before the All-Star break, then went on the disabled list from Aug. 5 to Sept. 24 because of elbow discomfort.
McCullers returned for the final week of the regular season and had three scoreless relief appearances, then had a 1.80 ERA in five relief outings during the playoffs.
He is 29-22 with a 3.67 ERA in 80 starts and three relief appearances over four seasons and was an AL All-Star in 2017.
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