Marshall, who left the game in the second half, has rushed for 24 yards on 12 carries this season.
The junior tore the ACL in his right knee in a game against Tennessee last year.
Georgia said Marshall suffered the injury to his "right lower extremity."
Five other Georgia running backs have rushed for more yards than Marshall this season, including Heisman Trophy candidate Todd Gurley.
The Bulldogs (2-1) host Tennessee next Saturday.