Cuban Yordenis Ugas pulled off a stunning victory over 42-year-old former champion Manny Pacquiao with a unanimous decision to retain his WBA welterweight world title in Las Vegas on Saturday.

The judges scored the fight 115-113 116-112 116-112 in favour of Ugas, who controlled the second half of the contest with his jab as the more aggressive Pacquiao struggled to land his punches on his return to the ring after a two-year absence.

Pacquiao, the only man in boxing history to hold world titles in eight different divisions and one of the greatest boxers of all time, said he is yet to decide if he will call time on his 26-year professional career.

"I don't know, let's just see," said Pacquiao, whose record dropped to 62-8-2. "Let me relax first and make a decision.

"I'm sorry I lost tonight, I did my best but my legs were very tight and that is why I couldn't move as well as I wanted."

Pacquiao was initially slated to fight WBC and IBF welterweight champion Errol Spence Jr, but a retinal tear in the American's left eye forced him to withdraw, with Ugas agreeing to step in at short notice.

Ugas had been elevated to WBA super champion after Pacquiao was stripped of the belt because of inactivity, as he had not fought since July 2019, and the Filipino looked desperate to get it back.

The clear favourite of the 17,438 fans at the T-Mobile Arena, southpaw Pacquiao came out aggressively in the early rounds with his trademark speed and combinations.

Ugas's long reach enabled him to keep the former champion at arm's length, however, and his jab was proving an effective, if not fight-winning, weapon.

Pacquiao continued to throw almost twice as many punches as his opponent, but the Cuban was more accurate with his, and there was plenty of sting in the big rights he was starting to land over the top.

The crowd was reduced to a nervous silence as the fight headed into the final rounds with no sign of the knockout that Pacquiao needed to come out a winner.

Ultimately, though, Pacquiao's ageing legs had nothing more to give and Ugas, a bronze medallist at the 2008 Beijing Olympics, earned the decision to improve his record to 27-4.

"Now the plan is to unify the title," Ugas, 35, said in the ring through a translator. "Everyone said he was the champion, now they know who the real champion is."

Pacquiao also said he would announce next month if he will run for the presidency of the Philippines next year. He had received a message of support from incumbent Rodrigo Duterte's administration.

"The boxing icon's loss in Las Vegas would not diminish the honours he bestowed to our country and the joy he gave to our people," presidential spokesperson Harry Roque said in a statement.

(Reporting by Manasi Pathak in Bengaluru; additional reporting by Karen Lema; Editing by Clarence Fernandez and William Mallard) ((Manasi.Pathak@thomsonreuters.com;))