If No. 10 USC’s recent loss to Pacific 10 Conference cellar-dwellers Stanford proved anything, it’s that they’re vulnerable. That’s why head coach Pete Carroll admits that it’s time to start over.

“”It doesn’t matter who you are, what your ranking is or any of that stuff,”” Carroll said in a weekly teleconference. “”If you give it up, you lose.””

The Trojans (4-1, 2-1 Pac-10) were ranked No. 2 before the loss to Jim Harbaugh’s team, who in July said of USC, “”They may be the best team in the history of college football.””

Harbaugh’s comments proved not only to be a stretch but a bogus overstatement.

After six weeks, the Trojans do indeed have some question marks. They were supposed to have about nine blue-chip runners, but only three – Stafon Johnson, Chauncey Washington and C.J. Gable – have done considerable damage, each having over 100 yards rushing.

“”All the talk early on about how many running backs we had was bogus since the start,”” Carroll said.

At quarterback, the Trojans are also a bit depleted.

Following Heisman Trophy candidate John David Booty’s four-interception breakdown against Stanford, USC will most likely send out sophomore Mark Sanchez in place of Booty, who has a broken finger.

Sanchez has thrown only 10 passes in his career. But if recent history has proven anything about USC quarterbacks, Sanchez was recruited for a reason.

Sanchez follows in the footsteps of Booty and recent legends such as Matt Leinart and Carson Palmer.

“”Mark is a terrific prospect,”” Carroll said. “”He came in highly regarded and has a big arm and a great energy about him. … It’s just a matter of experience. We’ve always been excited about Mark being a part of the team and what he can do. If he plays this week, we’re going to expect him to play great football.””

If Carroll is worried about his football team, he’s not showing it. After all, he’s had a knack for leading his teams to bounce-back victories year after year.

His teams have had five consecutive Associated Press top-four finishes, BCS Bowls, Pac-10 titles and 11-win seasons.

He said Monday he holds Arizona to an extremely high regard, but still expects “”to recover like we always do – to bounce back and put things back in perspective.””

“”Whether you’re on top or you’re trying to get back up, there are similar factors that weigh on you and we’ve dealt with them really well over the years,”” he added. “”I’m planning like we’re gonna do it well right now.””

The Trojans are 21-point favorites this week, following a week where they lost, despite being 41-point favorites.

The Wildcats have also played the Trojans tough in recent years. Last year at Arizona Stadium, with Leinart and singer Nick Lachey on the sidelines, the Wildcats lost 20-3, but the score was deceiving.

Arizona would have held USC to under 20 points for the first time in 55 games had punt returner Mike Thomas not muffed a punt deep in Wildcat territory, paving the way for a late touchdown. At halftime the score was 3-0 in favor of USC.

The previous year, the game was close throughout at the L.A. Coliseum, but USC scored three touchdowns late to pull ahead.

“”SC’s a real good football team and I’m sure they won’t be real happy, but that’s football,”” said UA head coach Mike Stoops. “”We just have to keep closing the gap little by little.””

USC defensive end Lawrence Jackson, who leads the Trojan defense with four sacks, and has 21 tackles (five for losses), said the fact that his team is 21-point favorite doesn’t change anything following last week’s loss.

“”We never play for point spreads or favorites or anything like that,”” Jackson said. “”We just go out there and play the way we need to play. … The key is execution.””