Corp participated in throwing drills again Wednesday, making dropbacks while wearing a helmet for the first time since sustaining a small break in a bone below his left knee Aug. 10.
"It just feels like I have more range of motion," Corp said after practice, holding his lightweight knee brace in his hand. "It's not restricting me at all. It keeps getting a little better each day. Today is the best it's ever felt."
Corp was chosen as the Trojans' replacement for Mark Sanchez out of spring ball, but was hurt in USC's second practice of camp. Barkley has led the first-team offense for much of the last week, and the Trojans' touted freshman looked sharp in Wednesday's workouts.
"It's definitely a competition, no doubt," Barkley said. "I don't know what the situation is right now, who's ahead of who. I feel like we're all putting forward a strong case."
Corp will participate in 7-on-7 drills Thursday, and will resume running this weekend. Coach Pete Carroll says the sophomore still has time to be ready for the Trojans' season opener against San Jose State on Sept. 5.
"This has been a great opportunity for Matt to be in charge and get some experience with that," Carroll said. "I'm just going to wait and see where it goes. I don't have a plan for this thing."
Carroll's decision defies planning because none of the three candidates has much game experience in the Trojans' system. Corp appeared briefly in five games last season. Mustain, who transferred from Arkansas after starting for the Razorbacks as a freshman, played in eight games as Sanchez's backup.
Barkley, who graduated early from high school so he could participate in spring ball, has received the most quality time in practice this month. Yet Mustain had much better statistics with the second-team offense in Monday night's scrimmage at the Coliseum, where Barkley went 5 for 18 with the starters.
The open competition is no problem for Corp, who seems upbeat despite his untimely injury.
"I still would have rather had a whole camp, but I think two weeks would give me enough time to prepare," Corp said of returning to practice next week. "It's always a competition. It never stops. You can never get complacent."
The Trojans also got good news on sophomore tight end Blake Ayles, who underwent minor surgery Wednesday to examine his heart arrhythmia. Carroll didn't know precise details about was discovered, but said Ayles should be back in practice "in a couple of days."