Manny Pacquiao's return to the ring has ended in a unanimous resolution defeat to Yordenis Ugas in their world welterweight title fight in Las Vegas on Saturday.

The 42-year-old Filipino was making his return to boxing for the first time since beating Keith Thurman in July 2019, going in as favourite against Ugas, who is seven years younger.

The Cuban, who took the fight on 11 days' notice following Errol Spence Jr's withdrawal due to an eye injury, used his jab wisely along with his agility and counter game.

Pacquiao appeared to lack his trademark speed and power while Ugas ensured he owned the middle of the ring early.

Ugas was awarded the unanimous decision victory 115-113, 116-112, 116-112 to defend the welterweight title which the World Boxing Association stripped from Pacquiao for "inactivity" earlier this year.

The victory improved Ugas' professional record to 27-4, while Pacquiao slips to 62-2-8, prompting discussion about his future in boxing given his age.

"I don’t know," Pacquiao said when asked about retiring after the fight. "Let me rest first and relax and make a decision if I continue to fight."

Pacquiao's work rate increased as the fight wore on, throwing better punches as the Cuban remained disciplined with his tactics.

Ugas' pinpoint right-hand hits troubled the Filipino throughout and he closed the fight strongly after a wild 10th round.

"It was a hard time, making an adjustment about his style and I think that was the problem for me because I didn’t make an adjustment," Pacquiao said.

"I congratulate my opponent Yordenis Ugas for making it tough tonight and winning tonight. That's boxing."

The fight was relatively even but Ugas insisted he deserved the win.

"A lot of respect for him, but I won the fight," Ugas said.