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PASADENA, Calif. -- When Anthony Barr roared through the line and hit Matt Barkley squarely in the No. 7 on his back, the roar rising out of the Rose Bowl was loud enough for a whole city to hear.

After so many years underneath Southern California, UCLA is on top of Los Angeles and the Pac-12 South, thanks to a first-year head coach and a freshman quarterback who don't realize they've done something that's not usual.

"Well, it is for me," Jim Mora said.

Brett Hundley passed for 234 yards and a touchdown and rushed for two more scores as No. 17 UCLA beat USC (No. 18 BCS, No. 21 AP) 38-28 on Saturday, clinching the Pac-12 South title and emphatically snapping a five-game losing streak in their crosstown showdown.

Eric Kendricks blocked a punt and made a fourth-quarter interception for the Bruins (9-2, 6-2 Pac-12), who overcame intermittent second-half rain and USC's star-studded lineup with a steady effort.

"When the season started, obviously nobody thought we were going to do what we're doing now," said Hundley, who was 22 of 30 and didn't throw an interception. "But we all knew deep down inside that we could do it, that we had the talent. We can do everything we set our mind to as long as we work hard."

Barkley, meanwhile, left the game with an apparent shoulder injury after Barr's sack and did not return.

He talked to the media after the game with his right shoulder hidden inside a sweater. The shoulder appeared to be supported by a sling. Barkley declined to discuss the injury, citing the program's policy on not disclosing injuries, and answered only three questions in an abbreviated news conference before being whisked away to the team bus by a school spokesperson.

"I thought I fought as hard as I could've fought," Barkley said. "I went down fighting. Plays were there, plays weren't there. There were times where I felt like I could've broken the game open. It just didn't happen."

A year after USC obliterated the Bruins 50-0 in a game that led to a coaching change in Westwood, UCLA punctuated its one-year revitalization under Mora with its first win over the Trojans (7-4, 5-4) since 2006 -- just their second in 14 years. The Bruins celebrated in the corner of the Rose Bowl and again with an impromptu dance-off in the locker room, even while Mora reminded them they've still got three games to play.

"It's a great moment, and I'm excited," said Mora, the winningest first-year coach in UCLA history. "I can't wait to hug my mom, shake my dad's hand and kiss my kids. I don't want to minimize it at all."

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Johnathan Franklin rushed for 171 yards and two touchdowns for UCLA, including a clutch 29-yard scoring run with 4:02 to play after USC trimmed its deficit to three points.

Shaquelle Evans had eight catches for 114 yards for UCLA, which clinched a spot in the Pac-12 title game in two weeks with its fifth consecutive win. The Bruins also played in that game last year, but only by default after finishing two games behind postseason-banned USC.

Everything has changed in Los Angeles this season: UCLA entered this showdown with a higher ranking and more victories than USC for the first time in a decade, and the Bruins backed it up.

"It's a great night, but we've got so many things we still want to do," Franklin said. "We're going to enjoy it, but we were confident coming into this game."

Barkley passed for 301 yards and three touchdowns, but threw two interceptions in the Trojans' third loss in four games. USC was the preseason's No. 1 team, but will return to the postseason in a lower-tier bowl after next week's regular-season finale against Notre Dame.

"You wouldn't think we would lose this game with a senior quarterback versus a freshman," USC coach Lane Kiffin said. "We're extremely disappointed with this season. We're too talented to have that many losses."

While Hundley led UCLA with the same preternatural calm he has shown all year, Barkley threw an interception on the game's first play and rarely looked comfortable. Barkley was hammered on the blind-side sack by Barr with 2:21 to play, spending a long moment on the Rose Bowl turf before walking off gingerly and watching USC's final drive from the sideline.

Nelson Agholor and Randall Telfer caught TD passes for the Trojans, and Curtis McNeal rushed for 158 yards. Marqise Lee had nine catches for 158 yards, and All-American Robert Woods had five catches for 68 yards.

"UCLA did a great job, but we're very disappointed," said Lee, who had a key early fumble. "We all knew about the stakes in this rivalry game, and we competed. ... Other people, they'll be sad. But to me, we came out against a great team and had too many turnovers."

Franklin and Joseph Fauria scored while UCLA jumped out to an early 24-0 lead under a morning mist that turned into serious rain by halftime at the Rose Bowl.

USC trimmed its huge early deficit to 24-20 on George Uko's fumble recovery in the end zone in the third quarter. The Trojans pulled within 31-28 with Lee's 14-yard TD catch and a 2-point conversion with 7:22 to play.

But Hundley and the Bruins coolly mounted an 83-yard drive, converting a long third down before Franklin -- UCLA's career rushing leader, nicknamed "Jet Ski" -- sped across the watery turf for the clinching score.

After Aaron Hester intercepted Barkley's first pass into double coverage, Hundley scored on a 1-yard keeper just 81 seconds in to give UCLA its first lead in the rivalry game since 2008. The interception was Barkley's 14th of the season, doubling his total as a junior and matching his mark as a mediocre freshman in 2009.

After Lee fumbled while curiously lined up as a tailback, UCLA went up 17-0 on Hundley's pretty fade to the 6-foot-7 Fauria. Franklin then made a 16-yard TD run up the middle in the second quarter.

A significant rain began to fall at halftime, and it immediately bothered the Bruins on a wacky play during their opening drive. Hundley and Franklin both fumbled before two diving linemen knocked the ball into the end zone, where Uko fell on it.

The teams both wore their home jerseys on the verdant Rose Bowl turf in a return to the distinctive tradition that was revived a few years ago. UCLA abandoned the tradition last year, inexplicably choosing its rivalry game to debut an all-white ensemble that hasn't been seen since its 50-point thrashing.