However, the fleet-footed Corp then won back the role during preparation for the Rose Bowl by eliminating mental mistakes and taking advantage of added weight and strength on what is now a 6-foot-4, 205-pound frame. "I've got the confidence," said Corp, who will be a third-year sophomore.
A more assertive presence in the huddle also has started to emerge. "Corp is starting to talk more and come out of his shell," tailback Marc Tyler said.
Only a little more than two years ago, Mustain was the starting quarterback at Arkansas as a freshman. After transferring to USC and redshirting in 2007, he spent most of last season as Sanchez's seldom-used backup.
During preparation for this year's Rose Bowl, he slipped to No. 3 and spent media day answering questions from reporters about whether he was considering another transfer.
Two weeks later, he is in the race to be the starter.
"It's exciting," Mustain said. "Things can change fast."
Green served as the No. 2 quarterback for one game last season but was used mainly on the scout team and is regarded as a versatile and key special teams player. He will be a senior next season.
Barkley is a wild-card in the mix. Had Sanchez stayed for his final season of eligibility, Barkley probably would have redshirted.
Now? "Without a lot of playing time on the other guys' plates, he gets to come in here and go head to head with these guys," Carroll said.
New offensive coordinator John Morton was disappointed that Sanchez left, knowing an experienced quarterback would have eased his transition.
But he didn't sound concerned. "You plug them in," he said of the quarterbacks. "You reload. You go."
With Sanchez, the Trojans were regarded as strong contenders for a berth in the Bowl Championship Series title game. A year after the defense finished as the nation's top-ranked unit, the offense was supposed to carry the load.
The Trojans still have nine returning offensive starters. And the transition at quarterback seemed to delight at least one other position group: the tailbacks.
Several spent last season frustrated over their roles in a rotation that produced more than 600 rushing yards for Joe McKnight, Stafon Johnson and C.J. Gable but a regular starring role for none. Sanchez's departure was received by some as a sign that the Trojans will move away from the pass and more toward the run.
