Green puts in a complete showing

The first throw was perfect, lofted down the sideline for a big gain. Then came a short completion and, two plays later, a scramble across midfield.

At a moment when all eyes were focused on the quarterback equation at USC, one guy came out and quickly showcased his skills.

Was it Mitch Mustain? Aaron Corp?

No, the reserve who announced his presence with authority to start Thursday’s scrimmage at the Coliseum was fourth-stringer Garrett Green.

The same Garrett Green who, in his first two seasons with the Trojans, has thrown all of one pass in a game. The same Garrett Green who has bounced around at safety and receiver.

“I just want to get on the field,” the junior said. “Regardless of what’s going on, I want to play.”

The only official completion of his career was a big one. In the 2008 Rose Bowl, Green caught a lateral from quarterback John David Booty, turned and heaved a 34-yard touchdown pass.

This summer, he expected to stick at receiver, a plan that flew out the window when starter Mark Sanchez injured his knee and the team needed another live arm in training camp.

“It took him a day to jump right back out there,” Coach Pete Carroll said. “He’s a great competitor.”

The official depth chart doesn’t even list Green at quarterback, but fans who have watched USC scrimmages might ask: Why not?

In three appearances, he has completed 20 of 35 passes for 263 yards with three touchdowns and three interceptions. On Thursday, while Mustain and Corp played against reserves, Green faced the starting defense.

“Garrett actually played really well,” Corp said. “Made some plays with his feet.”

Moving around the pocket to buy time. Scrambling downfield. At one point, he completed a pass while falling backward.

“It’s been fun slinging the ball around,” he said. “Just trying to make plays.”

His scrappy performances will probably land him right back at receiver when Sanchez returns. But his versatility -- he’s also on special teams -- could be handy during conference play when travel squads are limited in size.

“Down the road, he’s going to be a big factor for us,” Carroll said. “He can do so many things.”

Kids are all right

Offensive line coach Pat Ruel watched his reserves battle the first-string defense expecting to see missed blocks and blown assignments.

“I really didn’t see many,” Ruel said.

The second unit, stocked with freshmen such as Matt Kalil and Khaled Holmes, surrendered only one sack and led a touchdown drive early in the scrimmage.

“The young guys held their own,” Ruel said. “That’s a look at our future.”

Quick kicks

Tailback C.J. Gable did not participate but said he feels surprisingly good after straining his hip and ankle in practice this week. Cornerback Cary Harris, who injured his shoulder last week, expects to return to practice today. ... Carroll said defensive linemen Averell Spicer and Christian Tupou have played well enough to split time at nose tackle. ... USC fans saw the Coliseum’s new $2-million, high-definition video board for the first time, but the screen was not hooked up to high-definition cameras. Stadium officials said the picture will look sharper when the season begins.

--

david.wharton@latimes.com