LOS ANGELES - Dwayne Shackleford, normally doesn't get to play much, averaging 11.8 minutes and 2.9 points per game.
The senior from Washington, D.C., went scoreless in five first-half minutes Sunday night, but got his chance early in the second half when starting point guard Ryan Francis picked up his third and fourth fouls and went to the bench.
Shackleford made the most of his opportunity, getting 12 points and three assists in 16 second-half minutes, leading short-handed USC to a 71-68 upset over No. 15 UCLA.
''Shack's a good player,'' said Nick Young, who led the Trojans with 15 points and six rebounds. ''He's been in situations like that for a long time. I'm glad he stepped up like that tonight.''
Shackleford was 4-of-4 from the floor and 4-of-5 from the foul line, helping USC snap a season-high three-game losing streak.
''My policy is to just stay ready. I'm always ready to go,'' he said. ''Anything can happen. You can't be timid. I just play; I figure if I play hard, good things will happen. We just dropped three in a row. I'm just glad we got the win - we need that.''
USC won despite the absence of second-leading scorer Gabe Pruitt, who missed his third straight game due to an injured left knee. The Trojans had lost their previous three games to UCLA including a 66-45 setback at Pauley Pavilion last month.
''The biggest key was the minutes Shackleford gave us when Francis got his fourth foul,'' USC coach Tim Floyd said. ''I thought they physically manhandled us the last time we played them. I thought our kids responded.
Jordan Farmar had 21 points and five assists, Arron Afflalo scored 19 points, and Luc Richard Mbah a Moute had eight points and 10 rebounds for the Bruins (20-6, 10-4), who fell into a tie for first place in the Pac-10 with California.
UCLA has lost two straight after a five-game winning streak.
''First of all, give USC credit,'' UCLA coach Ben Howland said. ''Without Gabe Pruitt, they beat us. They had very, very good shooting and a lot of it was just beating us off the bounce. They played a very solid game. What really plagued us was turnovers.''
The Bruins turned the ball over 10 times in the first half and 14 overall.
USC entered the game having been outrebounded by an average of 10 per game in its last nine games, and was outrebounded 34-24 by the Bruins. But the Trojans shot 63.3 percent in the second half and 56.6 percent overall.
The Bruins shot 10-for-23 from 3-point range, but just 14-for-36 otherwise for a 40.7 percent overall performance. And they were just 10-of-18 from the foul line.
''This is the second game in a row we came out turning the ball over,'' Afflalo said. ''The pressure is probably what caused it. When you get in a game like this, you can't turn the ball over.''
Farmar scored five points and freshman Alfred Aboya four during a 13-0 run that gave the Bruins a 38-32 lead with 14:40 remaining. Francis went to the bench during the spurt in foul trouble.
But the Trojans responded, scoring the game's next 13 points to go ahead 45-38, and they were on top the rest of the way. Shackleford and Ndiaye scored four points each during the run.
Shackleford's three-point play with 4:15 left made it 58-47, and a foul shot by Stewart with 1:04 to go made it 65-55.
The Bruins battled back, getting two 3-pointers from Michael Roll and five points from Farmar during an 11-4 run, cutting USC's lead to 69-66 with 17.4 seconds to play. But Sead Odzic made a layup five seconds later to clinch the victory.
UCLA had one final chance to tie the game, getting the ball with one second left following a turnover. But Roll's pass to Afflalo was off target and rolled out of bounds as time expired.
Young scored six points and USC's other starters had at least one basket each as the Trojans took a 17-9 lead in the first 8 1/2 minutes.
Afflalo had all but one of UCLA's points before Farmar scored five straight and Mbah a Moute added a dunk, cutting USC's lead to 17-16. The Trojans led 29-25 at halftime despite being outrebounded 23-11.
The game was UCLA's 133rd and last at the Los Angeles Sports Arena, where the Bruins have a 105-28 record. They shared the Sports Arena as a home court with USC from 1959-65. Starting next season, the Trojans will play their home games at the new Galen Center on campus.