LOS ANGELES — It didn't take long for the post-Mark Sanchez era to begin at USC.

On Thursday, a few hours after the former Trojans quarterback announced that he was moving on to the NFL, former backups Mitch Mustain, Aaron Corp and Garrett Green moved in and supervised an informal passing-game workout that included newcomer Matt Barkley.

"The playing field," said Mustain, standing ramrod straight inside the gate of the Trojans' practice facility, "is even now."

Mustain was referring to the Trojans' quarterback derby, which will heat up when spring practice begins in March.

But USC opponents might be thinking the same as the continuity that marked Coach Pete Carroll's first eight seasons continued to splinter in a nationally televised news conference.

Sanchez's early departure was the latest in a string of recent exits from a program that produced seven consecutive Pacific 10 Conference titles. Offensive coordinator Steve Sarkisian and defensive coordinator Nick Holt both relocated to Washington after the Rose Bowl, taking a truckload of USC support personnel with them.

In Sanchez, Carroll lost a strong-armed, fiery leader, a Rose Bowl MVP and a potential Heisman Trophy winner.

"We've only really had good experiences with these kinds of transitions," Carroll said after the Trojans gathered for an afternoon team meeting. "So that's all we know. And hopefully we'll prove that again."

Carroll cited the torch-passing from quarterback Carson Palmer to Matt Leinart, from Leinart to John David Booty and from Booty to Sanchez.

But the next player who starts at quarterback for the Trojans under Carroll will be the first to do so without having to wait — and learn — for two or more years behind an incumbent.

On the plus side, the new quarterback will inherit an offense that returns every starting offensive lineman, every tailback and fullback and all but one receiver.

USC players said they would miss Sanchez's spirit.

"He's a great leader," center Kristofer O'Dowd said. "The next quarterback who's going to step up needs to come with that same enthusiasm."

Mustain, Corp and Green went up and down the depth chart last season while Barkley completed a stellar career at Santa Ana Mater Dei High.

"They come here to do great things and make big opportunities come to life," Carroll said. "Now, it's on."

Corp opened last season as Sanchez's backup but lost the position during a bye week after the second game.

However, the fleet-footed Corp then won back the role during preparation for the Rose Bowl by eliminating mental mistakes and taking advantage of added weight and strength on what is now a 6-foot-3, 205-pound frame. "I've got the confidence," said Corp, who will be a third-year sophomore.

A more assertive presence in the huddle also has started to emerge. "Corp is starting to talk more and come out of his shell," tailback Marc Tyler said.

Only a little more than two years ago, Mustain was the starting quarterback at Arkansas as a freshman. After transferring to USC and redshirting in 2007, he spent most of last season as Sanchez's seldom-used backup.

During preparation for this year's Rose Bowl, he slipped to No. 3 and spent media day answering questions from reporters about whether he was considering another transfer.

Two weeks later, he is in the race to be the starter.

"It's exciting," Mustain said. "Things can change fast."

Green served as the No. 2 quarterback for one game last season but was used mainly on the scout team and is regarded as a versatile and key special teams player. He will be a senior next season.

Barkley is a wild-card in the mix. Had Sanchez stayed for his final season of eligibility, Barkley probably would have redshirted.

Now? "Without a lot of playing time on the other guys' plates, he gets to come in here and go head to head with these guys," Carroll said.