LOS ANGELES—Lonzo Ball was rattled.

Three minutes into the second half, the freshman phenom looked up at the Galen Center rafters with a look that spelled frustration. Ball had just committed a turnover and thrown the ball away. He had then fouled USC's freshman De'Anthony Melton out of frustration.

As Bennie Boatwright, USC's best player, sat on the bench in slacks and a polo, UCLA's best player, and future NBA star, had an uncharacteristic night of a team-high seven turnovers forced by a USC defense that fueled their 84-76 upset win Wednesday night at home.

"[Lonzo] Ball is an outstanding player." head coach Andy Enfield said post-game. "You do the best you can on a player that talented."

After UCLA began the game on an 8-0 run fueled by center Thomas Welch who scored 10 points quicker than USC reached double digits, Enfield quickly pulled the trigger on their initial defensive gameplan and called an audible: USC switched from man-to-man defense to zone.

"We couldn't guard him," Enfield admitted afterward. "We were overmatched inside, and we needed to figure something out."

(Highlights by Connor McGlynn)

Fueled by the intensity of the raucous, sold-out Galen Center crowd, the game immediately turned from a potentially long night into a competitive rivalry game. USC responded and would go on to force 17 UCLA turnovers, five above their per-game average and the Bruins' highest total all season.

Thanks to the outside shooting of Shaqquan Aaron, who came off the bench and onto his favorite spot on the court to hit three three-pointers in the first half, USC's offense got the boost it needed to take advantage of its stellar defense.

"He was sensational," Enfield said of the transfer from Louisville who scored a game-high 21 points. "This was his best game."

Aaron's four three-pointers were a part of the Trojans' 14 shots from beyond the arc, which were a necessity to keep up with top-flight offense like UCLA. The Bruins came into the game with the best offense in the country, deadly shooters around the perimeter and a superstar in Ball that loves dishing out assists almost as much as draining long threes.

"We had to take care of the ball, because one of their strengths is to get out in transition," Chimezie Metu said.

Metu was a defensive force inside, protecting the rim one one end as well as he would rock it on the other end with various dunks and alley-oops. His stat sheet does not show it, but he would affect the Bruins' ability to get points in the paint, especially when the Trojans switched to zone.

Out on the edge, USC's perimeter players stuck like glue to the baby blue jerseys in front of them. As a result, UCLA shot 6-of-20 from three.

“We tried to take the three-pointers out of the game,” Enfield said. “The point of emphasis was to try and contest every three-point shot they took.”

USC players swarmed the outside as soon as UCLA touched the ball. In turn, they were not only able to give little space for shots, but also position themselves to make plays by deflecting the ball resulting in a whopping 12 steals.

USC's counterpart to Ball, at least on the floor Wednesday, was the stat-stuffing freshman Melton, who bothered Ball incessantly and totaled four steal himself. Melton measured up against the player many predict to be next year's top draft pick, making plays all over the court on his way to a 13-point, nine-rebound, five-assist night.

"He affects the game in anything he does," Enfield said of Melton. "I was surprised at how he could hold up and play with that intensity for so long"

Enfield and Co. have had no choice but to place freshmen like Melton in the spotlight. Injuries have depleted the depth of the team, but not enough to where their resolve and resiliency has been exhausted. On Wednesday night, there was plenty of it, even as UCLA came back to cut USC's 12-point lead to four in the second half.

With four minutes left, USC was on the brink of losing that lead when they forced three missed shots on one possession. Then, on their own possession, Metu and Stewart both gathered key offensive rebounds that exhausted the clock and all but sealed the victory.

"We prepared for them. We listened to our coaches and watched film," Aaron said post-game, holding a basketball that he said he would use to go shoot afterward. "We stayed composed."

The win is arguably Enfield's biggest win as coach of the Trojans. The atmosphere at the Galen the best he's seen. The victory for the program is the fourth straight against the crosstown rivals, who this time had a Top 10 ranking to their name.

“It’s rivalry game, of course you have a little bit more edge,” Aaron quipped.

“Crosstown rivals. It always feels good, not only beating them, but playing against them,” Metu echoed.

Enfield was hesitant to call the more than what it was: a much-needed conference victory. Players referred to it as a hopeful building block.

While the Galen Center crowd may have been raving about the upset, thanking their loud cheers for free Chick-fil-A and staying afterward to listen to Tusk and praise Enfield with rounds of applause, the team knows this is but a blip on the radar of what lies ahead.

It's a statement win that could become a boon for their season just as easily as it could prove to be a fallacious fluke.