LOS ANGELES — USC’s quarterback plot thickened Tuesday, but it’s too early to tell whether the developments will require a rewrite.

Starter Aaron Corp did not practice because of a bruised left knee suffered Monday. Freshman Matt Barkley took the first-team reps in Corp’s stead.
Although Barkley didn’t perform as well as in Monday’s practice, which he considers his best so far, he continued to make plays and a bid to start.
While wishing Corp a speedy recovery, Barkley said he viewed the redshirt sophomore’s absence as an opportunity.
“I’m hoping he gets back as soon as possible,” Barkley said. “But while he is out, I’m going to take advantage of every rep, every play, and try to get the most out of it that I can.”
When asked if Corp could lose his spot while he’s out, USC coach Pete Carroll said: “I don’t know why I would ever answer that question. I’m just going to go back and see what the deal is for tomorrow.
We’ve got to get him (Corp) back out here as soon as we can.”
Carroll then asked a reporter: “Are you asking me if this is the Wally Pipp situation relived? Is that what you’re saying?”
When the reporter said it was, Carroll declined to elaborate.
Corp said he hoped to return Wednesday. But he first will undergo an MRI exam to determine if there’s any damage beyond the bruise that doctors diagnosed after Tuesday’s practice.
Corp said the knee was swollen when he woke up and that he had too much pain and soreness to participate. He wore a brace for the first half of practice before applying an ice pack. He did say that the knee loosened up over the course of the afternoon.
Corp said he wasn’t worried about Barkley surpassing him but added: “I want to get back out there and compete all the time. We’re still preparing for this upcoming season. If I can’t practice, the less I can prepare.”
NOTES
Senior tailback Stafon Johnson sat out because of a stomach virus. ... Fullback Stanley Havili did not practice after banging his left shoulder Monday. ... Tailback Curtis McNeal returned after missing most of Monday when he had a tooth pulled just before practice. McNeal and fellow tailback Allen Bradford broke off long runs on a good day for the offensive line. ... Guard Jeff Byers and center Kristofer O’Dowd made the preseason watch list for the Outland Trophy, which goes to the nation’s best lineman. ... Freshman safety T.J. McDonald returned after missed two days because of a sprained ankle. ... USC basketball player Leonard Washington was among those watching practice. ...
The Trojans will practice in full pads Wednesday for the first time in camp.