Manny Pacquiao lost on his return to the ring after a two-year absence as Cuba's Yordenis Ugas upset the odds to win by unanimous decision and retain his WBA (super) welterweight title.
Ugas wasÂ only drafted inÂ on 10 August for the Las Vegas fight to replace the injured Errol Spence Jr.
It was Pacquiao's first bout since beating Keith Thurman for the WBA welterweight title in July 2019.
"I don't know," said Pacquiao, 42, when asked if it was his final fight.
"I need to relax and make a decision."
The eight-division world champion, who now has a has a record of 62 wins, eight defeats and two draws, added: "That's boxing.
"I had a hard time in the ring making adjustments. My legs were tight. I'm sorry I lost tonight, but I did my best."
Pacquiao, who is a serving politician in his native Philippines, was stripped of the WBA title in January because of inactivity.
Ugas beat Abel Ramos for the vacant WBA regular welterweight title in September 2020 before being elevated to WBA super champion after Pacquiao was stripped of the belt.
The 35-year-old had been preparing to make his first title defence against Fabian Maidana, but was promoted from the undercard to face Pacquiao.
Ugas dominated with his jab and clean punching to win on all three cards - 115-113, 116-112 and 116-112 - at the T-Mobile Arena.
"I'm very excited but most of all, I want to thank Manny Pacquiao for giving me this opportunity in the ring today," said Ugas, who now has a record of 27 wins and four defeats.
"We only had two weeks of training but I listened to my corner and it all worked out.
"I told you I am the champion of the WBA and I showed it tonight. A lot of respect for [Pacquiao], but I won the fight."