The roles are reversed for USC and UCLA heading into opening-round matchup at Pac-12 tournament

The last time USC defeated UCLA three times in a season, it was big news. Sports Illustrated may have even made it a cover story, had the magazine existed.

The year was 1954. That is why, when asked about the basketball adage that it is difficult to beat a team for a third time, USC guard Julian Jacobs responded with a shrug.

“We wouldn’t know,” he said.

After some thought, he added: “UCLA didn’t have trouble beating us three times last year.”

Wednesday’s first-round Pac-12 Conference tournament game between USC and UCLA will be unusual. USC, typically the also-ran in Los Angeles basketball, needs one final push to make the NCAA tournament. UCLA, a dominant force for decades, is more concerned about avoiding a losing record. The Bruins are 15-16. USC is 20-11.

The Trojans have defeated UCLA twice this season by a total 33 points, but they are not assured a spot in the NCAA tournament. For one of the few instances in this rivalry, UCLA can play spoiler.

“I’m pretty sure if we win, that would solidify our run this year, and we’ll get a bid in the tournament,” Jacobs said. “But say we lose, I think we’ll end up having to play in a play-in game or something like that. We really just want to beat UCLA.”

The teams have been on different trajectories since the start of the conference season. As each team prepared for the tournament, they offered contrasting moods: one hopeful, one mournful.

USC was picked to finish 10th in the conference in the preseason media poll. But the Trojans won four of their first five Pac-12 games, including a four-overtime win against Arizona, which was ranked No. 7 in the nation at the time. USC attained a national ranking this season for the first time since 2008. And the Trojans have won 20 games for the first time since 2009. Attendance at Galen Center was up nearly 30%.

UCLA started strong with wins over Kentucky, Gonzaga and Arizona but then regressed. Coach Steve Alford said this week that the Bruins had not improved since January. They lost five of their last six games.

And so, at practice this week, the differences were striking.

“We’ve had a terrific season,” USC Coach Andy Enfield said Monday.

“We’ve had an awful conference season,” Alford said Tuesday.

UCLA is not accustomed to such depths. At Pauley Pavilion, attendance declined at the end of the regular season. Against No. 9 Oregon last week, just 6,578 attended, well below UCLA’s season average. Some fans have even circulated a petition calling for Alford’s ouster.

“We all know it was frustrating,” the coach said. “The players feel it. The coaches feel it. We don’t like it. It’s unacceptable.”

UCLA’s struggles would make an upset win over USC on Wednesday sting even more.

USC makes the NCAA tournament in most current projections. As Enfield has noted several times this week, the Trojans have five wins against the top 50 teams in college basketball’s Ratings Percentage Index (RPI) and 11 against the top 100.

But they’ve also lost six of their last eight games. The selection committee could hesitate to select a team that has struggled down the stretch.

Enfield said “it would be nice” if USC made the NCAA tournament, but that wouldn’t make or break the Trojans’ season.

“I can’t be upset if we don’t achieve a certain goal,” Enfield said, “because they’ve improved and they’ve worked hard and they’ve done their best. That’s all I can ask as a coach.”

UCLA point guard Bryce Alford said USC’s tournament situation “doesn’t matter to us.”

But it has historical significance. The last time USC made the NCAA tournament when UCLA did not was 1985, when the format was expanded to 64 teams.

USC has reached the Final Four twice, and both times it defeated UCLA three times along the way.

Asked whether he agreed with Jacobs on the importance of beating UCLA, Trojans guard Elijah Stewart balked.

“I’m trying to win as many games as possible,” Stewart said. “We have such a good team this year, it’s like, why limit yourself to one?”

zach.helfand@latimes.com