LOS ANGELES -- There's another good college basketball team in Los Angeles, and No. 8 UCLA found out the hard way.
Shaqquan Aaron scored a career-high 23 points off the bench, and Southern California matched its season best with 14 3-pointers in an 84-76 upset of the Bruins on Wednesday night.
Elijah Stewart added 15 points for the Trojans (18-4, 5-4 Pac-12). They beat their crosstown rival for the fourth straight time, having swept all three meetings last season including in the conference tournament.
"It's important for our season and what we're trying to do," USC coach Andy Enfield said.
Isaac Hamilton scored 20 points and Lonzo Ball had 15 points and 10 rebounds for the Bruins (19-3, 6-3), who have lost two in a row for the first time this season. They were beaten 96-85 by then-No. 7 Arizona at home last week.
"I hate losing," Ball said. "We've got to turn things around."
The Bruins became the fifth team in the Top 10 to lose in the last two days. No. 1 Villanova, No. 2 Kansas and No. 4 Kentucky lost Tuesday night, and No. 6 Florida State joined UCLA in losing Wednesday.
Ball committed a season-worst seven of UCLA's 17 turnovers, one off its season high.
"We gave up too many things off our own mistakes," UCLA coach Steve Alford said.
Aaron, in his first season after transferring from Louisville, and Stewart had four 3-pointers apiece for USC. The Bruins were just 6 of 20 from long range.
"You just have a little more energy when you play them," Aaron said. "It helps when shots start falling early."
After trailing by 15 points early in the second half, UCLA rallied to get within four twice.
The first time, USC answered with consecutive 3-pointers by Aaron and Jordan McLaughlin.
"We stayed composed," Aaron said. "Some games we have let some teams come back. Tonight we got stops. They hit some shots but we stayed in the game."
After Aaron Holiday's three-point play drew the Bruins to 66-62, the Trojans responded with power.
Stewart dunked one-handed when De'Anthony Melton's jumper hit the rim, and Chimezie Metu stormed through the lane for a two-handed jam and the foul. He made the free throw, Melton hit the Trojans' 14th 3-pointer -- matching their total in a win over Arizona State last weekend -- and Metu made two free throws to push their lead to 76-65.
"A lot of uncontested shots and they were getting easy shots with dunks and layups," Hamilton said. "Guys are coming at us with everything they've got and we've got to do the same."
UCLA was held well under its scoring average of 93 points per game. Holiday finished with 15.
The Bruins outscored USC 20-10 to start the game, with 7-footer Thomas Welsh scoring 10 points and leaving the Trojans clearly overmatched inside.
USC dumped its man-to-man and switched to a zone for the rest of the game.
"Once they went zone, we had a hard time finding him (Welsh) because there was no 1-on-1 matchup at that point," Alford said. "Turnovers really hurt us in the first half and we kind of dug ourselves a hole."
Melton hit a 3-pointer that launched a 40-18 run by the Trojans over the rest of the half. They made six more 3-pointers, Metu dunked three times and Melton capped a fast break with a jam.
"When we settled down our offense realized we could get any shot we wanted," Metu said.
The Bruins repeatedly lost the ball on tipped passes in the paint, leading to 13 turnovers in the half, five by Ball.
"Put this loss on my back," the touted freshman said. "I'll take it."
UCLA: After four teams ranked ahead of them lost in the past two days, the Bruins probably blew a chance to move up.
USC: The Trojans play five of their final nine regular-season games on the road, including a rematch with UCLA on Feb. 18.
UCLA held a closed-door meeting for nearly 30 minutes after the game, with the seniors doing the talking.
"When adversity hits, everyone gets in their shell and nobody really talks," said Hamilton, one of two senior starters. "That hurts."
Ball added: "Coach is frustrated, we're frustrated. We'll get back in the lab and we'll bounce back."
The Bruins have five days of practice before they play their next game.
UCLA: Starters TJ Leaf and Bryce Alford both had off nights. Leaf scored eight points on 4-of-10 shooting and Alford had just three points, going 1 of 7 from the floor. ... Once the Bruins lost the lead on a 3-pointer by Aaron and trailed 29-28, they never got it back. ... UCLA shot 48 percent from the field and outrebounded USC 37-36.
USC: The Trojans had 12 steals, led by Melton with four. ... They are off to their best start since also going 18-4 to open the 1992-93 season. ... Football coach Clay Helton attended the sold-out game, as did former USC quarterback Matt Leinart and NFL Hall of Famer Cris Carter.
UCLA: Visits Washington State next Wednesday, followed by Washington three days later to complete a stretch of three straight road games.
USC: Visits Washington next Wednesday.