USC's depth, its much discussed potential Achilles' heel, is already being tested before the first preseason practice.

Senior defensive end Devon Kennard may be lost for the season after suffering a torn pectoral muscle. He will undergo surgery next week, a source told ESPNLosAngeles.com's Pedro Moura, and will be out at least two to three months.

Redshirt freshman Greg Townsend is listed as Kennard's backup on the preseason depth chart. While the Trojans welcomed back 22 starters from 2011, they lost three on the defensive line, perhaps the Trojans' thinnest position.

More here on what this means for the Trojans.