A reminder was served on Wednesday night, in a rough and rowdy sequence near the end of the first half. After a UCLA foul, Coach Steve Alford yelled and stomped on the sideline. The officials whistled him for a technical foul, UCLA's first all season. The crowd stirred.
Then, a minute and a half later, USC forward Bennie Boatwright fouled UCLA guard Prince Ali hard on a breakaway layup. The officials ruled it a flagrant 1. The UCLA student section chanted words unprintable in this newspaper. The USC fan section yelled back.
This rivalry has lacked intensity in years past. No more. USC was making a statement: The Trojans can't be taken lightly anymore. They delivered the message with gusto in an 89-75 blowout victory.
With a minute left in the game, from a corner of Pauley Pavilion, USC's fans sang the tunes one sings after a big win.
"Na na na na, hey hey hey, goodbye."
Goodbye, UCLA, and goodbye three seasons of futility.
The win is almost certain to vault USC (15-3, 4-1 Pac-12 Conference) into the top 25 for the first time since 2008. It is USC Coach Andy Enfield's first win over UCLA, and Alford's first loss to USC, in five tries. It marks USC's best start since 1993, and, temporarily, at least, a shift in Los Angeles basketball dominance east across I-10.
"It's big," guard Katin Reinhardt said. "We're not the same team we were last year at all."
UCLA's fans began to file out even before the game ended. The team's coaches sat on the bench, hands propping up chins.
All game, USC found yawning holes in UCLA's transition defense. Midway through the first half it ran out to a 13-0 run. When the Trojans made the last basket of the half, their lead had swelled to 18.
USC played faster and smarter. UCLA's three-point defense was exposed. USC, which leads the conference in three-pointers made, added another nine, on 20 attempts.
Guard Jordan McLaughlin led USC with 23 points.
USC's top six scorers all average in double-figures. Forward Chimezie Metu is the first player left in single-digits. But on Wednesday, he came alive. He scored 21 points with eight rebounds, both career highs.
Before the game, Enfield had expressed concern over UCLA's rebounding prowess. He has called UCLA forward Tony Parker and center Thomas Welsh the two best offensive rebounders in the conference. But with Metu's ascendance, and a team-wide effort on the glass, USC outrebounded UCLA 42-39.
"He played a huge game," McLaughlin said of Metu.
For UCLA (11-7, 2-3), the loss continued a vexing season, in which it has beaten some of the nation's best, but sits just four games above .500. The loss ended a 12-game Pac-12 home winning streak.
The problems, again, started on defense. UCLA was buoyed by the return of forward Gyorgy Goloman, who played his first game of the season after suffering a stress fracture in his leg. But UCLA was sluggish in transition.
"The majority of our losses are because we can't guard," Alford said. "You score 75 points at home, you should win."
Added Welsh: "I don't think we're bringing that energy on defense, and that's really hurting us."
In the opening minutes of the second half, USC extended its lead to 21. Then UCLA mounted a rally. The Bruins pounded the ball inside to Parker and went on a 10-0 run. With more than 13 minutes left, Parker muscled in a layup to cut the lead to 10. The crowd came alive again. Parker flexed at midcourt. USC called timeout.
The Trojans halted the run, momentarily, but UCLA returned, again and again, to Parker. His dunk with about five minutes remaining shrunk USC's lead to single digits.
USC was unmoved. One minute after Parker's dunk, McLaughlin buried a three-pointer, and the Trojans never looked back.
It was a quiet night for UCLA guard Bryce Alford, who scored nine points on four-of-13 shooting, but Parker was a force. He scored 27 points, making 12 of 18 shots, and added 12 rebounds.
Afterward, Andy Enfield, as he did after USC defeated Arizona last weekend, tried to downplay the significance of the win.
"This was obviously an important win for us," Enfield said. "We try to take every game and put equal importance on it."
Metu, at least, was willing to say what Enfield wouldn't.
"I think we can make a push to win the league," he said.
Follow Zach Helfand on Twitter: @zhelfand