Mitchell suffered the injury this week in practice.
The Valdosta native moved to cornerback in the offseason after playing receiver as a freshman in 2011. The move was Mitchell's decision, but was a welcome sight for a secondary short on depth and dealing with suspensions.
Mitchell, who has spent limited time on offense this preseason as well, was likely to start opposite Branden Smith in the opener. Damian Swann, Devin Bowman, freshman Sheldon Dawson and Blake Sailors the remaining listed players at the position.
Senior Sanders Commings, who started every game in 2011, is the suspended for the first two games stemming from an offseason arrest.