The seldom-used backup quarterback for USC had the opportunity to transfer without penalty when the NCAA handed down sanctions against the university in June.
Despite the presence of incumbent starter Matt Barkley, Mustain chose to remain with the Trojans for his final season of eligibility.
The Arkansas native showed again on Saturday that he is prepared to play if called upon.
In a scrimmage that was mostly dominated by the Trojans’ first-unit defensive line, Mustain completed 23 of 35 passes for 231 yards and a touchdown playing almost exclusively with and against second-unit players.
Mustain also starred in the Trojans’ final spring scrimmage, passing for nearly 300 yards and five touchdowns at the Coliseum.
“I feel good with where I’m at,” said Mustain, later adding, “I feel like I could execute whatever we have in week to week.”
Coach Lane Kiffin said that Barkley remains the starter but that Mustain’s command of the offense provides the coaching staff with the unusual luxury of using a single play-call sheet for games rather than tailoring individual ones for the starter and backup.
“A lot of times with your backup quarterback you have another sheet because he can’t do everything,” Kiffin said. “I’m excited about Mitch’s performance again.”
Barkley started slow before finishing nine of 15 for 127 yards with a touchdown. The sophomore faced a swarming first-unit defense and did not benefit from as many calls for short pass plays as Mustain did.
“We were kind of experimenting in the first half a little bit with the offense, doing a couple plays that we normally don’t do,” Barkley said. “In the second half we came out and just stuck to what we’ve been doing and what we know best and it worked.”
Tight end Jordan Cameron had the standout performance of the scrimmage, catching eight passes for 96 yards.
Cameron, a senior, switched from receiver to tight end in the spring. He has added 20 pounds to his 6-foot-5 frame and weighs about 250 pounds.
“I feel more powerful, more confident in my ability as a blocker,” he said. “In the spring I was like