Backup quarterbacks pick up the pace

USC’s final practice before the Trojans’ first in full pads took on a palpable sense of urgency Saturday as quarterbacks Mitch Mustain and Aaron Corp battled for a possible starting job in place of injured Mark Sanchez.

Sanchez suffered a dislocated left kneecap Friday, an injury less serious than a possible season-ending ligament tear. But the fourth-year junior’s availability for the Aug. 30 opener at Virginia and beyond is up in the air.

The opportunity has infused Mustain, a transfer from Arkansas, and Corp, a redshirt freshman. Both consciously asserted themselves as if they were the starter.

“It gives you a little shot,” Mustain said. “The way you prepare doesn’t really change, but it does give you that little edge.”

Mustain and Corp both had their moments on a day when the Trojans concentrated on third-down situations.

“I think I’m in a good spot right now,” Corp said. “I just have to keep consistent, keep doing well.”

Coach Pete Carroll said Mustain and Corp would be evaluated on an ongoing basis. For all the good plays each made, bad ones were not a surprise.

“There’s obviously some times when they’re struggling with the installation and they’re thinking [too much],” Carroll said. “That’s totally what should happen.”

Sanchez, who will begin rehabilitation Monday, stayed close. With his left leg elevated, he drove a cart to different areas of the practice fields to watch and offer encouragement.

“He’s yelling at guys and trying to get his two cents in,” Carroll joked.

Sanchez said his knee felt better and that he was mostly encouraged by dozens of phone calls and text messages from well-wishers and others who wanted to relay recovery stories. Projections regarding his return ranged from 10 days to four weeks.

“I’m hoping mine will be like all the shorter ones I heard,” he said.

Speaking from experience

Sophomore center Kristofer O’Dowd sat out six games last season after suffering a dislocated kneecap against Washington.

O’Dowd required surgery because of cartilage damage. Sanchez’s injury is not believed to be as serious, but the quarterback still had questions for O’Dowd, who told Sanchez, “It’s going to feel like you tore your ACL or something because it’s going to hurt on the side and then in the middle. You’re fine. It’s just the soreness.”

O’Dowd could not help noticing the cart Sanchez was driving.

“I never got a cart,” he quipped. “I didn’t even get a crutch.”

Green day

Junior Garrett Green donned a yellow quarterbacks jersey and will work at the position until Sanchez returns.

Green played quarterback and defensive back at Sherman Oaks Notre Dame High. As a freshman at USC, he moved to safety early in the 2006 season and then switched to wide receiver last season.

“It comes back to you pretty quick,” he said of returning to quarterback. “I have a different dynamic with the receivers now, so it’s pretty cool.”

Green’s 34-yard touchdown pass to Desmond Reed off a lateral in the Rose Bowl gives him more completions for the Trojans than either Mustain or Corp, who have yet to take a game snap.

Quick kicks

The Trojans will practice for the first time in full pads tonight at 7:30. “We go under the lights -- they’re going to have a blast,” Carroll said. . . . Cornerback Cary Harris intercepted a pass and broke up several others. . . . Running back Marc Tyler said he did not practice because of a concussion. . . . Joe McKnight said he tried to match Adam “Pacman” Jones of the Dallas Cowboys, who caught six punts without putting a ball down. “I got to four but I couldn’t get the other two,” McKnight said. . . . Sanchez, when asked if he had a sleepless night Friday, said he had dozed in the MRI exam machine after he was injured. “I woke up and thought I was in a bad dream,” he said. “I was like, ‘No!’ And then it all sunk back in and I was like, ‘Man.’ But it could be a lot worse. I should be thankful.”. . . Freshman cornerback T.J. Bryant sat out because of a skin irritation, according to Carroll. . . . Los Angeles District Attorney Steve Cooley and Carmen Trutanich, a candidate for Los Angeles City Attorney, attended practice.

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gary.klein@latimes.com