The undefeated regular season is complete, but for the No. 1 USC men’s water polo team, its biggest challenge lies ahead.

The Trojans (24-0, 8-0) used two clutch goals to pull ahead late on Saturday, hanging on to win 10-9 over crosstown rival UCLA (24-3, 6-1) during a rare night game at McDonald’s Swim Stadium.

“We really didn’t have any breathing room the whole game,” senior driver Michael Rosenthal said, “but we came out with a win so that’s all that matters.”

Rosenthal’s hat trick led the scoring effort for the Trojans, while junior driver Nikola Vavic, senior two-meter Matt Burton and junior utility Mace Rapsey added two goals apiece.

“He [Rosenthal] hadn’t been as aggressive as he should lately, so it was great to see his performance,” USC coach Jovan Vavic said. “He’s got great confidence now.”

The first half was a back-and-forth affair, with the Trojans breaking away from an early 3-3 tie to take a 6-4 halftime lead. The Trojans made it 7-4 just 22 seconds into the third period with a flip shot from Vavic. But No. 2 UCLA wasn’t done just yet.

The Bruins scored three straight goals, two of them by leading scorer Paul Reynolds, and tied the match at 7 before Burton got one back for the Trojans before the end of the third.

Then, UCLA got a power-play strike from defender Chris Wendt to even the match and put USC in an unfamiliar position.

For the first time in 15 games, the Trojans were tied in the fourth period. That didn’t last, as Rosenthal skipped a shot under Rapacz’s outstretched arm to give the Trojans a 9-8 lead.

“I just had to take a shot,” Rosenthal said. “I looked the goalie off a little bit and put it in.”

Later in the period, a pinpoint Rosenthal cross and resounding Rapsey strike later, and the Trojans were up 10-8.

“It felt great,” Rapsey said. “It was such a good pass so I could just pop it in.”

UCLA’s Daniel Lenhart quickly responded to make it 10-9 with 28 seconds left, but the Trojans kept possession for the rest of the contest.

“When they tied the game, we really had to buckle down and find a way to make sure we got stops most importantly, as well as find a way to score a goal,” Rosenthal said. “I’m sure glad we did.”

Vavic, though pleased, pointed out areas in need of improvement.

“We gave up too many goals,” Vavic said. “There were situations where we didn’t block because our blockers didn’t cover their space.”

The win clinches USC’s regular season conference title, giving it the top seed for the Mountain Pacific Sports Federation championships, where it will face UC Santa Barbara on Friday.