AFTER SHOCK

Before the season, USC’s game against Arizona was regarded by most as a comfortable way for the Trojans to end the first half of the schedule and an opportunity for players and their families to enjoy parents weekend at the Coliseum.

That all changed with last week’s stunning loss to Stanford.

Tenth-ranked USC is now out to prove that one of the biggest upsets in college football history was a fluke and that it is still a contender for a record sixth consecutive Pacific 10 Conference championship and the national title.

“We look at USC as a hungry and mad team,” Arizona Coach Mike Stoops said.

That could also describe USC fans who booed the Trojans during their 24-23 loss to 41-point underdog Stanford. The shocking defeat ended a school-record 35-game home winning streak and the six-year tailgate party it fostered.

“We had a game that we wish we could forget but we can’t,” USC Coach Pete Carroll said.

With the first Bowl Championship Series standings coming out Sunday, Trojans players said they intend to get back on track. They will attempt to do so amid questions about a team that also played poorly against Washington before falling to Stanford.

“We’re excited to get out there and prove the world wrong,” offensive lineman Jeff Byers said. “We just have to go show everybody who we are.”

USC (4-1 overall, 2-1 in the Pac-10) could look different this afternoon with Mark Sanchez making his first start at quarterback.

The third-year sophomore from Mission Viejo will replace John David Booty, who suffered a broken finger and had four passes intercepted against Stanford.

Booty is available today, but Carroll hopes to rest the senior so he can continue to heal.

Meanwhile, Sanchez will try to capitalize on the opportunity.

“I think I’m ready for it,” he said.

So do his teammates.

Middle linebacker Rey Maualuga said Sanchez’s week of practice was his best since they arrived together as freshmen in 2005.

“He’s trying to get that starting job and keep it,” Maualuga said. “He shined. He won’t look back after this.”

Senior tight end Fred Davis, who had become Booty’s go-to receiver, said, “John David has more experience so you trust him more, but the more confidence Sanchez gets the better he’s going to play. So it will help if we just all do our part.”

Sanchez will be making his first start since a high school all-star game. He has a strong arm and has never shied from trying to make plays with it in practice, sometimes with spectacular results, other times with interceptions.

“We want him to play a nice calm football game and get the ball to the players that need the football, and see if he can execute the offense like we always want to,” Carroll said.

Carroll is counting on the USC receiving corps to aid Sanchez after it hurt Booty and the offense with multiple drops and poor route-running against Stanford.

The Trojans once again are expected to be without leading rusher Stafon Johnson, who has not practiced for two weeks because of a left foot bruise and sprain. Senior Chauncey Washington will start at tailback for the fourth consecutive game, and Carroll said sixth-year senior Hershel Dennis would be his main backup.

The offensive line, still without injured regulars Chilo Rachal and Kris O’Dowd, could be in for more changes, especially if senior center Matt Spanos cannot snap effectively because of stitches in his right hand.

Byers might be forced to start at center, with Alatini Malu and Zack Heberer at guard and Sam Baker and Drew Radovich at tackle.

Against Stanford, the Trojans gave up a season-high four sacks, converted only seven of 19 third downs and turned the ball over five times.

The miscues shortened the field for the Cardinal and put pressure on a Trojans defense still searching to create turnovers characteristic of past USC teams under Carroll.

USC’s defensive line is hoping to mimic Oregon State’s, which sacked Arizona quarterback Willie Tuitama eight times last week in a 31-16 Beavers victory that dropped Arizona to 2-4 overall and 1-2 in the Pac-10.

The Trojans’ secondary is looking to bounce back after surrendering two huge fourth-down receptions last week during Stanford’s game-winning drive.

Tuitama, a junior, has passed for 15 touchdowns in Arizona’s new spread offense and is much more experienced than Stanford’s Tavita Pritchard, who beat the Trojans in his first start.

USC safety Taylor Mays said Tuitama “seems like a whatever-means-necessary kind of guy.”

The Trojans would like to adopt a similar personality.

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gary.klein@latimes.com