Mario Barrios retained the WBC welterweight championship after a majority draw against Manny Pacquiao on his comeback to the ring.
The 46-year-old Pacquiao was ahead going into the 10th round in Las Vegas, but all three judges scored the final three rounds for his younger opponent.
Two judges scored the draw, but the third gave Barrios a 115-113 victory.
Pacquiao entered the fight aiming to break his own record as the oldest welterweight champion, which he set in 2019 at age 40.
Barrios entered as the betting favourite but failed to deliver a convincing victory.
"I thought I won the fight," Pacquiao said in the aftermath of the loss.
"A close fight. My opponent was very tough. A wonderful fighter."
Barrios, a 30-year-old from San Antonio, hoped to bounce back from a split-decision draw on November 15 against Abel Ramos, but didn't exactly come away with an emphatic victory in improving to 29-2-2.
The heavily pro-Pacquiao crowd loudly booed the decision.
"It was an honor to share the ring with him," Barrios said. "This is by far the biggest event I've had to date, and we came in here and left everything in the ring. I have nothing but respect for Manny.
"His stamina is crazy. He's still strong as hell and his timing is real. He's still a very awkward fighter to try to figure out."
In the night's co-main event, Sebastian Fundora retained his WBC super welterweight title after Australian Tim Tszyu did not come out for the eighth round of their rematch.
