LOS ANGELES — A loss isn’t just a loss for Southern California these days, it’s a major upset. That’s the way it goes for a team that’s been so successful.

One of the most damaging setbacks occurred two years ago, when UCLA stunned then-No. 2 USC 13-9 at the Rose Bowl to bounce the Trojans out of the national championship game. The schools meet in Pasadena for the first time since then on Saturday, and the Bruins have another opportunity to play spoiler.

“I know a lot of guys on the team remember that game and still have a bad taste in their mouths,” USC guard Jeff Byers said Tuesday.

“Our team gets kind of lax at times. Coach (Pete Carroll) does a very good job of expressing to us that this team could be a snake in the grass,” Trojans defensive tackle Fili Moala said. “We can’t let that happen again.”

The Trojans had scored at least 20 points in 63 straight games and beaten their crosstown rivals seven consecutive times before the surprising setback, one of just 10 losses in 94 games for USC since the beginning of the 2002 season.

“They’ve all been the same,” Carroll said. “I mean, all of these games, anybody can beat you and can win. No matter what everybody thinks is supposed to happen, you’ve got to go play the football game.

“They played great defense on that day, we couldn’t move the football. They had a couple plays that put them in scoring position, and that’s all they needed.”

As big an upset as that might have been, this would be even bigger should it happen. The Trojans were 33-point favorites Tuesday, believed to be the largest point spread in the history of the rivalry.

“If you remember back to that game, like some other games when we’ve struggled, we struggled early,” Carroll said. “The format of that game was reminiscent of the Oregon State game. Same kind of thing happened, although we played much better defense (against UCLA).”

Carroll referred to USC’s 27-21 loss as a 25-point favorite at Oregon State on Sept. 25 that has proven to be enough to eliminate the Trojans (10-1, 7-1 Pac-10) from immediate national championship contention.

“There’s always like the what-ifs,” Moala said. “We don’t have anyone to blame but ourselves.”

A victory over the Bruins will give USC an unprecedented seventh straight Pac-10 title and a fourth consecutive appearance in the Rose Bowl game.

“It’s home, I wouldn’t want to be anywhere else,” Moala said. “It’s the Rose Bowl.”

UCLA (4-7, 3-5), playing under first-year coach Rick Neuheisel, has lost three of its past four games, including a 34-9 setback at Arizona State last Friday.

“DeWayne Walker is a really good football coach,” Carroll said of UCLA’s defensive coordinator. “He has had tremendous success. You can’t tell by the score, but the defense played like crazy (at ASU). They looked loaded up, fired-up, well-schooled, great intensity and all that. That’s what gives any team a chance to beat somebody.”

The Bruins allowed only 122 yards at ASU, their best defensive performance since the 1989 Cotton Bowl against Arkansas. The Sun Devils scored all four of their touchdowns on defense — three on interception returns and the fourth on a fumble return.

Carroll said the Trojans will wear cardinal jerseys Saturday, violating an NCAA rule that requires visiting teams to wear white jerseys. The last time USC and UCLA both wore home jerseys was in 1982, when they shared the Los Angeles Coliseum.

USC will pay a cheap price — a timeout following the opening kickoff.

And that’s it.

“For a number of years, I’ve been hoping to get back to this tradition that stood a long time ago, of both schools wearing their home jerseys when they played here in town,” Carroll said. “It just didn’t work out for one reason or another. Honestly, the first time I had the thought was the very first year. I thought it would have been not a classy deal to just surprise UCLA and wear our home jerseys. I just wanted to get back to it.

“I’m just willing to go ahead and make the statement that we want to go for it. I hope everybody understands. This is also an invitation of course to UCLA to do that when we play (at the Coliseum) as well. I don’t know how they’ll handle that, but I would think they’re considering it.

“It always looked awesome, it was just a part of the matchup and the spectacle, kind of playing for rights here in Los Angeles and in Southern California. So hopefully everybody will get something out of it. Maybe I’m getting in trouble by doing this, I don’t know.”

Carroll won’t be in trouble with UCLA. Fact is, school spokesman Marc Dellins said, the Bruins are in favor of the teams’ wearing their home jerseys in the rivalry, and to express that approval, they’ll call a timeout to even the playing field after USC is penalized with the loss of its first timeout.