Boogie Ellis and USC make a case for the NCAA tournament with their win over UCLA.

There wouldn’t be many more shots like this. For USC, a team just rounding into form, opportunities to state its case to the NCAA tournament selection committee were so sparse from here it couldn’t afford to squander any left. Least of all against its bitter rival, UCLA, one of the few Pac-12 teams capable of catching the committee’s attention.

It was with those stakes on his shoulders that Boogie Ellis stepped back from the top of the key Thursday night and let a final-minute three-pointer fly. Just a few weeks ago, when the two crosstown rivals last met, it was Ellis who unraveled down the stretch, committing an inexplicable offensive foul that turned the tide late.

This time, the Trojans point guard would be his own one-man tidal wave, sweeping away UCLA with a second-half effort that might rank among the most memorable in the recent history of the rivalry. This time, with Ellis in search of redemption and USC in search of a statement, the furious comeback would not fall short in a 77-64 victory over UCLA.

“We needed a big statement win,” USC coach Andy Enfield said.

USC got just that on Thursday, handing UCLA its second consecutive defeat and its fifth straight loss at Galen Center. The Trojans sit just a game behind the Bruins in the Pac-12 race, a possibility that seemed unlikely a few short weeks ago.

UCLA remains in the driver’s seat in that regard, having won 14 straight before its current losing streak. But the Bruins’ lackluster effort in the second half left plenty of questions in their wake. Namely why their offense has abandoned them in back-to-back second halves against USC.

“We’re no juggernaut,” UCLA coach Mick Cronin said. “I didn’t harbor any illusions about going undefeated in the Pac-12.”

For David Singleton, there a simple answer as to why UCLA once again fell apart after halftime.

“In my opinion, I think they wanted it more than us,” said Singleton, who scored 14 points. “I think they played harder, they wanted it more, they got their job done.”

By the time Ellis fired off that final three on Thursday, USC was already well into unleashing a second-half barrage on UCLA, burying the Bruins with deep shots and suffocating them on ball screens.

UCLA had been in full control at halftime, clinging to a healthy lead, seemingly one prolonged run from putting the Trojans away.

But this time, it waited too long. This time, Drew Peterson hit a three. Then freshman Tre White. Then Ellis. And Ellis. And Ellis again.

Over the final 17 minutes on Thursday, USC hit 13 of its final 20 shots, seven of which came from its point guard, who went off for 27 points in the second half.

“That’s a pretty special game,” Enfield said.

There was little UCLA could do to slow down Ellis. His 27 second-half points matched the Bruins’ entire team total after halftime, as Enfield called one isolation play after another for his point guard.

“When he gets it going, he’s really hard to guard,” Enfield said. “He played like a first-round draft pick tonight. It was very impressive.”

He wasn’t exactly as awe-inspiring before halftime, having missed his first five three-point attempts of the game.

Both he and Peterson were a combined four of 12 before the half as UCLA sailed to a commanding early lead. They’d finish with a combined 47 points.

USC had no answer in the first half for freshman forward Adem Bona’s strength on the interior.

Nor could it slow down Singleton’s shooting stroke from beyond the arc, where he contributed four three-pointers.

“We were getting killed at halftime, just like the first half at Pauley last time,” Peterson said.

But once again, the Trojans regrouped at the break. They shut down Bona, holding him to a single shot.

They closed down the lane, clogging up any drives for point guard Tyger Campbell, who didn’t make a field goal after half.

They expelled more effort on the boards. Then, Ellis went nuclear, firing away until finally just one last basket was required.

That’s when the point guard pulled up, with freshman Amari Bailey in his face. The shot found only net, handing USC its biggest win of the season — and a major statement ahead of March.

“This is a start,” Ellis said. We still have more to prove. Winning one game against UCLA, it’s great. It’s great for the rivalry. But we still have more to prove.”