Quarterback derby heats up at scrimmage

USC’s quarterback competition ramped up Sunday, though not to the extent that statistics from the Trojans’ first scrimmage might indicate.

Sophomore transfer Mitch Mustain, who is trying to overtake Mark Sanchez, passed for three touchdowns against reserves, including a 70-yard strike to receiver Ronald Johnson on Mustain’s first play. But Mustain struggled in two series against the first-team defense.

Meanwhile, Sanchez got off to a slow start in his first series before leading the first-team offense to three scoring drives against the first-team defense.

Coach Pete Carroll praised Sanchez, Mustain and Aaron Corp after the 78-play scrimmage but acknowledged that to accurately compare them, “You have to get them against the first guys to see what’s really going on.”

Nevertheless, it was a confidence-building day for Mustain, who had been looking forward to the opportunity to show the skills that helped him go 8-0 as a freshman starter at Arkansas in 2006.

Mustain completed seven of nine passes for 137 yards, including another touchdown to Johnson that covered 31 yards and a 10-yard touchdown pass to fullback Adam Goodman.

“Mitch can make plays – there’s no doubt about it,” Carroll said.

Mustain and Sanchez said last week that they considered the scrimmage a midterm exam of sorts.

Asked to grade himself afterward, Mustain said, “probably a C-plus,” citing the need to improve game management skills, especially in the second half of the scrimmage when fatigue began to set in.

Sanchez was nine for 15 for 106 yards but did not throw a touchdown pass. He gave himself a “B-plus, A-minus,” saying, “I felt I had good control out there.”

Carroll agreed.

“He got going and looked very much in command,” the coach said.

Corp completed four of eight passes for 51 yards with one interception.

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Junior safety Taylor Mays briefly lost consciousness after tackling tight end Anthony McCoy on a 34-yard pass play from Sanchez.

“I got a little shook up, but people from Seattle, they’re bred tough,” said Mays, a Seattle native who was named to Playboy’s preseason All-America team.

Mays and McCoy were scheduled to be examined for possible concussions.

Asked if he had given thought to turning pro after the end of the 2008 season, Mays said, “I can’t lie and say I’ve never thought about it. But I’ve talked to my coaches and I’ve talked to my parents and I feel like the best thing for me right now is just to focus on this season so I don’t miss out on anything … on any opportunities on getting better. And then, obviously, at the end of the season we’ll evaluate.”

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Nose tackle Averell Spicer, who has been sidelined because of a knee injury, said he would probably have arthroscopic knee surgery this week or next… . Tailback Allen Bradford scored on runs of 73 and two yards… . C.J. Gable gained 52 yards in three carries… . Johnson caught three passes for 113 yards… . Clay Matthews had four tackles, including three sacks. Derek Simmons had two sacks, Christian Tupou and Trey Henderson one each… . The Trojans resume workouts Tuesday.

gary.klein@latimes.com