LOS ANGELES – It’s a doomsday scenario that few at the University of Southern California are comfortable talking about.

USC is at or near the top of preseason polls, positioned for a run at the Bowl Championship Series title, largely because of the senior’s decision to postpone NFL plans for a final season with the Trojans.

Barkley sat out one game in 2009 and another in 2010, the Trojans losing both.

If Barkley were to be sidelined this season, the Trojans would turn to Max Wittek or Cody Kessler. For more than a year, the redshirt freshmen have been competing to become Barkley’s backup and possible successor.

Coach Lane Kiffin has said he would name one the No. 2 quarterback before the Sept. 1 opener against Hawaii.

“They’ve really become very focused about this – and you see it,” Kiffin said. “For two guys who’ve never played in a game, I think they’re doing great.”

Wittek, from Santa Ana Mater Dei High in Orange County, Calif., and Kessler, from Bakersfield Centennial in California, both enrolled at USC in January 2011. They played catch-up to 2009 signee Jesse Scroggins, but injuries and academic issues sidelined Scroggins for long periods, enabling the younger quarterbacks to close the gap.

Scroggins transferred to El Camino College in June, making it a two-player competition.

Barkley notes their improved performance.

“They know as much, if not more than I did when I was their age in terms of defense and protections,” Barkley says.

Quarterbacks coach Clay Helton also sees maturity in the quarterbacks’ meeting room.

“I can’t fool them anymore,” he says. “I don’t think I’ve gotten them all camp with trick questions.”

Wittek has undergone a physical transformation in his 1 1/2 years at USC. Already rangy upon arrival, he now stands 6-foot-4 and weighs 245 pounds.

And, “I don’t feel like I’ve lost a step at all,” he says.

Wittek is recognizing defenses faster and has displayed improved arm strength during training camp.

Regardless of Barkley’s presence, he says he has always prepared as if he were a starter. The competition with Kessler won’t end, he notes.

“As far as I’m concerned,” he says, “my competition with Cody or anyone else who is here will never end as long as we’re here.”

In a separate interview, the 6-foot-1, 215-pound Kessler echoes Wittek.

After the 2010 season, Kessler worked diligently to eliminate a hitch in his throwing motion. He spent this summer working tirelessly to lengthen his stride while dropping back.

“We don’t go out and just compete against each other – we’re pushing Matt,” Kessler said. “And the coaches have said, ’Whoever gets the backup this year doesn’t mean that they’re going to be the next starter.’”

Wittek and Kessler say they will be ready if called upon.

Kiffin, while praising their improvement, is not looking for a backup to perform like a seasoned veteran.

“Not really expecting him to go in and light it up,” Kiffin says. “You really want to make sure he can manage the game.”

USC’s quarterback corps is expected to grow next spring with the anticipated addition of Max Browne, a highly regarded prospect from Skyline High in Sammamish, Wash., who has committed to the Trojans. Browne reportedly is working to graduate early so he can enroll in January.

But Wittek and Kessler will have the edge.

“When the time comes,” Barkley says, “they’ll both be able to lead this team.”