Rush, a 6-foot-3, 292-pound senior, suffered the injury during Saturday's intrasquad scrimmage and had surgery on Monday in Birmingham.
"He broke a small bone in his leg and it's an enormous loss," Crowe said. "Odie had become the emotional leader of that offensive line."
Rush was just one of two Gamecocks (quarterback Marques Ivory) to start all 12 games on offense last season. Crowe said redshirt freshman Tarik Milner has been moved up to the starting spot on the offensive line.
Jacksonville State, which finished 9-3 and made the FCS playoffs last season, kicks off the 2011 season on Sept. 1 against OVC rival UT Martin.