Separation Saturday for quarterbacks?

It’s midterm time for USC’s quarterbacks.

The competition to win the starting job reaches an important milepost today when the Trojans scrimmage at the Coliseum. It will be the eighth of 15 spring workouts and is the only scheduled practice in the stadium until the finale April 25.

“It should be kind of a test date for us,” Coach Pete Carroll said.

Aaron Corp, Mitch Mustain and Matt Barkley are the main focus of the exam.

Corp, a redshirt sophomore, leads the competition and has a recent history of performing well in spring scrimmages at the Coliseum. In 2008 he completed 13 of 16 passes for 158 yards and two touchdowns on the last day of spring workouts.

“It’s a bigger atmosphere with the Coliseum and just more of a game-type situation,” he said. “You’re actually moving the ball, so it helps you get in a groove a little bit. . . . It’s a big day.”

Mustain says he won’t approach the workout any differently than usual. The venue is larger and crowd noise will be piped in, but the junior does not intend to change his focus.

“It’s nice to be in the Coliseum, but other than that it’s the same stuff,” Mustain said.

Barkley, a freshman, is coming off perhaps his best practice to date. He also attended last year’s mid-spring scrimmage at the Coliseum, so he is accustomed to the surroundings and the Trojans’ routine.

Barkley, however, knows that all eyes, especially those of Carroll and quarterbacks coach Jeremy Bates, will be on him. “They’ll be looking, definitely, at how I speak up and do all that stuff,” Barkley said.

Carroll is confident Barkley will continue to perform well, regardless of the setting.

“I don’t think it’s going to affect him at all,” Carroll said. “The way Matt has handled everything, I think he’s going to take the next step just like the other guys.”

Senior Garrett Green has mostly played receiver and on special teams and is regarded mainly as a backup quarterback..

Quick hits

The competition for the third receiver spot could heat up today. Junior David Ausberry and sophomore Brice Butler have made the most high-profile plays, but Jordan Cameron, Travon Patterson and Brandon Carswell also have had their moments. . . . The scrimmage begins at 11:30 a.m.

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gary.klein@latimes.com