LOS ANGELES — Maybe Pete Carroll just wants to have some fun, to keep former assistants Steve Sarkisian and Nick Holt guessing as Washington prepares to play USC.

Or perhaps Carroll just can’t help himself when it comes to all things Matt Barkley.
Whatever the reason, Carroll declined Thursday to name a starting quarterback for USC’s Pacific 10 Conference opener Saturday at Seattle.
But with Barkley still sidelined because of a shoulder injury, third-year sophomore Aaron Corp will almost certainly make his first collegiate start.
“This is what he’s been preparing for all along,” Carroll said after practice. “It’s been in his mind that he’s the starter.”
So what’s going on in Carroll’s mind?
With Barkley possibly sidelined, running back Joe McKnight trying to overcome illness and safety Taylor Mays nursing a knee injury, Carroll is not about to provide his former offensive and defensive coordinators with any concrete information that would help them hone their game plan and pull off an upset.
The Trojans also are coming off an emotional victory over Ohio State, the same scenario that contributed to a letdown and loss in their Pac-10 opener last season at Oregon State.
Carroll, therefore, appears to be doing everything possible to sharpen his players’ competitive edge.
His quarterbacks included.
“Aaron knows he’s ready to go,” Carroll said. “I’ve told him, `Get ready. You have to be thinking and preparing like you’re starting the football game.”’
That seemed obvious as Barkley did not practice for the fourth consecutive day.
The freshman threw passes to the team trainer, but his range of motion remains impaired by a bone bruise in his right shoulder suffered during last week’s dramatic 18-15 victory at Ohio State.
Barkley spoke with Carroll after practice, pointing to his shoulder throughout the conversation.
“He’s got a bruise that’s really, really tender, that’s right in the place where you fire,” Carroll said. “And when you throw, it activates.
”But it’s not something that he’s going to hurt more ... other than the fact that if he really changes his motion, then things like that can give him a sore arm in other areas. So that’s one of my concerns.“
Another would be the fact that Barkley has not thrown a pass in practice since engineering the Trojans’ game-winning drive at Ohio Stadium.
Asked whether he had ever started a quarterback who had not practiced during the week, Carroll said he twice started Drew Bledsoe in similar circumstances when he coached the New England Patriots. The Patriots split the two games, Carroll said.
Bledsoe, however, was a seasoned veteran. Barkley has two college starts under his belt.
That, of course, is two more starts than Corp has made since arriving at USC from Orange Lutheran High School in 2007.
The mobile Corp redshirted his first season and finished the 2008 season as the backup to starter Mark Sanchez.
He entered training camp No. 1 on the depth chart after throwing only one interception in 15 spring workouts and beating out Barkley and junior Mitch Mustain.
But Corp’s chance to succeed Sanchez vanished when he suffered a cracked fibula on the third day of training camp, opening the door for Barkley.
Corp completed all four of his passes and led two fourth-quarter scoring drives in USC’s 56-3 season-opening victory over San Jose State. He warmed up but was not called upon after Barkley played through his shoulder injury last week.
Offensive coordinator John Morton has no doubt that Corp is ready to play.
”He was the starter from the get-go and he brings an extra dimension with his legs, which is a threat to the defense,“ Morton said.
Several USC players said they had no preference between Barkley and Corp, but they sensed that Corp would lead them against Washington.
”It would be rare to see Barkley come back to start without practicing all week,“ center Kristofer O’Dowd said. ”I think Aaron’s running the show.“
Carroll remained noncommittal. ”It just depends on how far (Barkley) comes along and all that,“ he said. ”Hopefully, we won’t do the wrong thing.“