‘Sluggish’ offense is source of concern

The timeline for USC quarterback Mark Sanchez’s return from a knee injury took on an added sense of urgency Tuesday after an unimpressive performance by the Trojans’ offense during a scrimmage at the Coliseum.

Granted, it was the first time that Aaron Corp and Mitch Mustain were at the controls with a chance to possibly start the Aug. 30 opener. But the offense scored only once in 11 series -- and those points came on a touchdown pass from emergency back-up Garrett Green to receiver Brandon Carswell.

“We didn’t get much done today, very sluggish,” Coach Pete Carroll said of the offense.

That might be a testament to a defense that is expected to be one of the best in the nation, but the first unit was rarely on the field in its entirety.

Corp, a redshirt freshman, got three series with the first-team offense. He completed six of 13 passes for 60 yards and scrambled four times for 42 yards.

But Corp also fumbled two snaps, including one inside the 20-yard line.

“We made some mistakes, obviously,” Corp said. “We turned the ball over in the red zone. That can never be good.”

Mustain (nine of 13 for 94 yards) got only one series with the entire first-team offense and that ended with an interception by freshman Brian Baucham near the goal line on the final play of the 57-play scrimmage.

Carroll maintained he was not worried about the offense -- “It’s too early to be concerned about anything right now,” he said -- and described the scrimmage as “a really good first outing for us.”

Meanwhile, Sanchez was encouraged after team physician James Tibone examined his left kneecap. Sanchez said his rehabilitation would become slightly more aggressive and that he still hoped to return for the opener.

“I’m off the crutch and things are going well,” he said.

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Revenge factor

The scrimmage had an element of payback for a defense that felt as if it had surrendered too many big plays in practice this week.

“The offense really gashed us,” defensive end Kyle Moore said, recalling the team’s first night in full pads Sunday.

This time, defensive coordinator Nick Holt wanted better tackling and liked what he saw. His squad didn’t do anything fancy, but Holt said the intensity was high and missed assignments were few.

Linebacker Malcolm Smith made four tackles and eight players made three each. Moore collected one of four sacks and the defense deflected four passes.

Holt praised his freshmen linemen -- Armond Armstead, Malik Jackson, Wes Horton and Jurrell Casey -- who got plenty of reps against a depleted offensive line.

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For what it’s worth

The first-unit offensive line remained consistent with Kristofer O’Dowd at center, Thomas Herring and Zack Heberer at the guards and Butch Lewis and Charles Brown at the tackles.

Lingering injuries dictated the lineup. Still, with coaches juggling the line in practices, the players appreciated some consistency.

“It’s nice getting used to each other,” Lewis said.

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Quick kicks

Travon Patterson caught four passes for 49 yards. . . . Defensive end Everson Griffen (hamstring) and tight end Blake Ayles (concussion symptoms) were among the players who did not participate because of injury or precautionary measures.

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gary.klein@latimes.com

david.wharton@latimes.com