The Trojans need McCoy, one of their most productive players, because backup tight end Blake Ayles won't play because he also hurt his ankle. Ayles has struggled while stepping in for McCoy, who's caught 16 passes for 375 yards this season.
Williams, probably the best receiver in the Pac-10, is also leading the conference in punt returns. Redshirt freshman Brice Butler will replace Williams at receiver, while running back Joe McKnight will return punts.
On the plus side of the ledger, playmaking fullback Stanley Havili, who's been out with a shoulder injury, will start.