University of South Florida defensive tackle Cory Grissom suffered a fractured fibula in his right ankle during Monday morning's non-contact practice as the Bulls entered their final week of spring drills.
Grissom, a 6-foot-2, 316-pound rising senior who has started 25 consecutive games, will have surgery Thursday.
The timetable for his return is unknown, but it could make him questionable for at least the start of the 2012 season.
Sophomore Todd Chandler was listed as Grissom's backup on USF's initial spring depth chart.
Last week, USF coach Skip Holtz spoke in generalities as he listed priorities for spring football.
"You want to get in a lot of good work and get better,'' Holtz said. "You want to find out about different guys. The one thing you don't want to do is have somebody get hurt.''