LOS ANGELES -- The Pac-10's highest-ranked team of the season came calling, and Southern California found the motivation it often lacks against lesser opponents.
Nikola Vucevic had 25 points and 12 rebounds, and his teammates came up with two huge blocks in the closing minutes to help Southern California upset No. 10 Arizona 65-57 on Thursday night.
"We get more fired up for better teams and we play more aggressively," he said.
Did they ever.
Jio Fontan added 21 points and Alex Stepheson had 12 points and 10 rebounds for the Trojans (16-12, 8-7 Pac-10), who extended their winning streak to a season-best three games and beat a top-10 team for the first time since knocking off No. 9 Tennessee in December 2009.
"Keep going, don't let up," Fontan said. "It was a big confidence boost that helps out our résumé."
Jesse Perry scored 12 points and Kevin Parrom added 10 for the Wildcats (23-5, 12-3), whose eight-game winning streak ended on an off night for offensive star Derrick Williams, who scored a season-low eight points.
"Honestly, I think it was good for us to lose," Williams said. "We were getting too big-headed, thinking we can beat everybody, we can beat anybody. I'm kind of glad we lost and came down to earth."
The Wildcats head into a Saturday showdown at second-place UCLA, which routed Arizona State 71-53 to climb within a game of the top spot.
"You never want to go on the road and lose two straight, especially when you're ahead by two games in the conference going into the last four," Williams said. "But [USC is] a great team as well. This is the same team that beat Texas at home by 20, that went to Kansas and lost by one or two, so their record may not show it, but they're a great team."
Williams scored well less than his average of 19.7 points per game, second best in the league, and it was the first time he was held to single digits this season. He grabbed 11 rebounds while playing with a wrap protecting his bandaged right pinky finger.
"He's the best player in the Pac-10, and you want to do better than him," Vucevic said. "We did a good job as a team stopping him."
The Wildcats were held below their Pac-10-leading averages in field goal percentage, 3-point percentage and points scored on the road. Williams and Lamont Jones, who were a combined 12-for-12 from the floor against USC in a win Jan. 29, were a combined 6-for-23 in the rematch.
"This is the hard part about the stretch run of the season," Arizona coach Sean Miller said. "You earn all the praise and you get it, but you forget that there are some really hungry teams waiting for you."
Neither team led by more than four points until the waning minutes. Vucevic hit a pair of free throws to tie it at 56-all with 2:37 remaining.
After Stepheson blocked Jones on a drive, Stepheson got fouled and made both free throws to put USC ahead 58-56.
Jones got denied again on Arizona's next possession, with Marcus Simmons coming up with a big block.
"I just didn't want to give up on the play. Luckily, I blocked it," Simmons said.
Vucevic was fouled again and made both, extended USC's lead to 60-56 as the crowd chanted, "Go SC!" with 58 seconds left.
"Vucevic is a beast inside. He really raised his stock a lot and a lot of it had to do with me," Williams said.
Fouled by Simmons, Kyle Fogg made the second of two free throws to leave Arizona trailing by three with 40 seconds left. Parrom and Williams missed on the same possession, forcing the Wildcats to foul the rest of the way.
"It comes down to the fact that we had two assists on 19 field goals," Miller said. "It's alarming to have two assists."
The Wildcats fell to 1-4 at Galen Center. The Trojans, whose field goal percentage defense of .411 is second best in the league, held Arizona to 36 percent.
Williams didn't score his first basket until there was 5:15 left in the half, giving the Wildcats their largest lead of eight points.