PASADENA, Calif. - Southern California’s dejected players trudged off the Rose Bowl field, oblivious to the celebration going on around them.

Their national championship hopes had just ended with the biggest upset of the season.

UCLA knocked No. 2 USC out of the Bowl Championship Series title game with a stunning 13-9 victory over its crosstown rival Saturday. The Bruins did it with a vastly improved defense and a quarterback starting on three days’ notice.

“Give credit to UCLA. They made it a difficult day,” said USC coach Pete Carroll, whose team lost for just the fourth time in its last 59 games. “They kept us from doing what we wanted to do. We had no rhythm. We did not anticipate this happening.”

Neither did most fans of either team. The Trojans hammered the Bruins 66-19 last season to lock up a second straight appearance in the BCS title game, and figured to win again, if not by such a one-sided score, to make it three in a row.

It wasn’t to be, even though USC came in averaging 32.3 points a game.

Besides having their national championship hopes ended, the Trojans (10-2, 7-2 Pac-10) had their NCAA-record streak of 63 games in which they had scored 20 or more points snapped.

And a lot of the credit goes to UCLA’s first-year defensive coordinator DeWayne Walker, a former Washington Redskins assistant. It was his schemes the Trojans were unable to solve.

“I didn’t believe it until the clock hit zero,” UCLA coach Karl Dorrell said. “All we wanted to do was stay close and get a chance to win. I know how important this win is for the Bruin family. I know that it’s been a long time.”

Since 1998, to be exact. The Trojans had beaten the Bruins seven straight times. Before that, UCLA beat USC eight times in a row.

College football How all 32 games are shaping up

The Bruins only sacked USC quarterback John David Booty twice, but they had him on the run throughout and forced him to throw several balls away. And they held Trojans star Dwayne Jarrett to four catches for 68 yards.

“We gave them a lot of different looks,” Walker said. “If we confused Booty, that would take care of Jarrett.”

The strategy worked to perfection.

“Their offensive line was real wide-eyed,” UCLA defensive end Bruce Davis said. “People said we’re small. That’s all right. We were big enough to knock Booty on the ground.”

Slideshow   The Week in Sports Pictures The Giants on top of the football world, getting ready for the London Olympics and more. more photos

Jarrett said his timing was affected by the Bruins’ pass rush.

“They did a great job or switching up their defensive schemes and bringing pressure,” he said.

Minutes after the game, and with a crowd of 90,266 still roaring, UCLA’s Junior Taylor, Chris Markey and Dennis Keyes jumped the bandstand, grabbed cheerleaders’ megaphones and led the delirious fans in cheering for the upstart Bruins.

Patrick Cowan passed for 114 yards and ran for another 55 as UCLA paved the way for a Michigan-Ohio State rematch or an Ohio State-Florida matchup for the national championship Jan. 8 in Glendale, Ariz.

As Pac-10 champions, the Trojans will return to this same field on New Year’s Day and play in the Rose Bowl game. The final BCS standings and bowl pairings will be announced Sunday.