Quarterback Mitch Mustain waiting for his chance with Trojans

As quarterback Mitch Mustain walked off the Coliseum field this week, a fan's voice echoed throughout the stadium: "We're pulling for you, Mitch!"

But is USC's coaching staff?

With Aaron Corp sidelined because of a leg injury, Mustain has been relegated exclusively to backup duty while freshman Matt Barkley has taken every first-team snap in the Trojans' two scrimmages.

"Who knows?" said Mustain, who was 8-0 as a freshman starter at Arkansas in 2006. "Maybe they'll give me a shot in practice or a scrimmage. I'll be excited when the opportunity comes."

On Tuesday, less than 24 hours after Mustain's second efficient scrimmage performance, the hoped-for opportunity once again failed to materialize as Barkley took nearly every first-team snap.

Coach Pete Carroll has praised Mustain's recent performance -- he completed 24 of 32 passes for 262 yards and two touchdowns without an interception in the scrimmages -- but when asked Tuesday if the junior would receive a chance to work with and against starters, Carroll said, "Right now, it's so important to develop Barkley. Because of what he's shown us, we have to give him every opportunity in the event Aaron doesn't make it back."

Barkley struggled in Monday night's scrimmage but practiced with confidence Tuesday after reviewing the film.

"I'm glad that didn't happen during the season," he said of his five-for-18 performance.

Corp has been sidelined for eight days because of a cracked fibula. On Tuesday, he dropped back and threw passes during one drill.

"It's just a matter of being confident enough to drive onto my front leg," he said.

X-rays taken Tuesday revealed that Corp's leg was healing, so the third-year sophomore might be able to return to practice next week.

As the Trojans prepare for their Sept. 5 opener against San Jose State, that probably means even fewer snaps for Mustain, who has more college game experience than any Trojans quarterback.

Mustain plans to be ready if called upon. "I just have to keep playing," he said.

Front and center

Alex Parsons arrived at USC in 2006 as a defensive lineman. Three years later, he is the Trojans' starting center.

At least for now.

Parsons, a 6-foot-4, 300-pound senior from Irvine, moved into the spot after Kristofer O'Dowd suffered a dislocated right kneecap during Monday night's scrimmage. An MRI exam showed no need for surgery. An athletic department spokesman said O'Dowd was expected to be sidelined two to three weeks.