With the top seed in the Pac-12 tournament on the line, USC fell for the first time in 14 months in the regular season finale against its crosstown rival.

The No. 1 Trojans (25-1, 6-1) fell to No. 5 UCLA (21-2, 7-0) 3-4 in a battle at a packed Marks Stadium between two teams undefeated in conference play. By taking the final three singles matches, the Bruins upset the Trojans and snapped their 45-match win streak that began last February.

Denied · Freshman Eric Johnson and the Trojans were unable to win their 46th straight match as UCLA came out victorious, 4-3. - Chris Roman | Daily Trojan

UCLA’s Adrien Puget, ranked No. 61 in singles, clinched the Bruins’ victory by denying No. 43 freshman Yannick Hanfmann’s comeback attempt in a 7-6 (5), 3-6, 6-2 win.

USC had established a 3-1 lead after doubles play and after seniors Steve Johnson and Daniel Nguyen, ranked No. 2 and No. 17, respectively, defeated their opponents in straight sets in their last matches at Marks Stadium.

In between their victories, No. 23 Ray Sarmiento relinquished a point to the Bruins with his 3-6, 4-6 loss to No. 21 Nick Meister.

By the time Nguyen finished off UCLA’s Dennis Novikov for USC’s third point, however, the three Trojans on courts 4 through 6 were all trailing in the third set of their respective matches.

USC sophomore Emilio Gomez, ranked No. 50 in singles, was up 5-4 in the second set with the first set secured and nearly locked up another point for USC. His opponent, No. 86 Marcos Giron, however, powered back, eventually taking a 4-6, 7-5, 6-1 win.

UCLA’s Dennis Mkrtchian also rallied back in a 4-6, 6-3, 6-2 finish over freshman Roberto Quiroz to deadlock the score at 3-3.

Once Quiroz dropped the final set of his match, all eyes shifted focus to court 5, where Hanfmann was already down 2-5 in the third set against Puget.

Hanfmann could not battle back, and the Bruins emerged from the match with a perfect conference record and the top seed in the upcoming Pac-12 tournament.

“It’s a tough loss to UCLA. We need to learn from it and just keep working hard,” Nguyen said. “Take them out at the Pac-12 [Tournament] — that’s the plan.”

Despite the loss, Nguyen, who will graduate with seniors Johnson and Ben Lankenau next month, expressed his appreciation for his final match at Marks Stadium.

“I can’t really explain it. It was definitely a very special moment for me,” Nguyen said. “It was great seeing my family come and watch my last match and seeing my friends support me.”

Johnson agreed, and even conceded that the one blemish to the Trojans’ nearly undefeated season could be “a blessing in disguise.”

“Daniel and I have been looking forward to this moment for forever,” Johnson said. “The outcome obviously wasn’t ideal, but I think it’s going to be a good thing in the long run. I think everyone is going to work a lot harder.”

The Trojans look to bounce back in the conference tournament, which begins Thursday in Ojai, Calif.

With the second seed, USC will have a bye for the first two rounds before beginning play in the semifinals Friday.