McAvene had Tommy John surgery and will be out until the middle of the 2022 season, Kyle Glaser of Baseball America reports.
It's unclear when he underwent the procedure, but it was likely sometime this winter or early spring, given the recovery timeline. McAvene had a chance to distinguish himself as one of the Cubs' top pitching prospects this season, but he will be nearing his 25th birthday when he is able to return next season and has yet to pitch in a full-season league.