Manny Pacquiao blamed a shoulder injury for his defeat by Floyd Mayweather in Las Vegas, claiming it stopped him from using his right hand.
American Mayweather, 38, outclassed his Philippine rival at the MGM Grand and was awarded a wide unanimous decision.
Pacquiao, 36, said he thought he did enough to win the fight, despite most observers agreeing with the verdict.
'Three weeks before the fight I got a tear in my right shoulder,' he said. 'It got better but it wasn't 100%.'
Mayweather started the brighter of the two and rocked Pacquiao with a number of right hand counter punches in the early exchanges.
The Filipino came back at the American in the fourth round, stunning Mayweather with a left hand and again in the sixth round but was never able to back it up and Mayweather ran out a comfortable winner on the judges scorecards.
Pacquiao said he wanted to have an injection in the shoulder before the fight but the Nevada Athletic Commission refused.
Pacquiao's promoter, Bob Arum, claimed he informed the Commission of the injury five days ago and defended the decision not to cancel the fight, the most lucrative in boxing history.
'Athletes always fight hurt and we felt the work that was done on the shoulder during training would enable him to use his right hand,' said Arum.
Commission chairman Francisco Aguilar said he first knew about the injury two hours before the fight, whe.