Fletcher, a third-round pick, started for the third straight game and was injured in the second half of Sunday's 42-6 loss to the Colts. He'll require two operations and coach Steve Spagnuolo said Monday he might not be ready for the start of next season.
Long snapper Chris Massey also is set for knee surgery that will sideline him the remainder of the season. The team was auditioning potential replacements on Monday.
Offensive guard Richie Incognito will be out this week with a ligament injury to his right foot. Tackle Adam Goldberg is likely to move to Incognito's spot, with rookie Jason Smith starting at right tackle.