Floyd Mayweather, who won the much-hyped "fight of the century" on Sunday, has rubbed salt into the wound of his opponent Manny Pacquiao.

The 38-year-old American posted a picture of himself on his Instagram account on Wednesday with a caption that read: "19 years in the fight game and I've had one excuse: 'Don't have an excuse'. Winners win and losers have excuses."

That was seen by many as a thinly-veiled jab at Pacquiao, who claimed that a shoulder injury cost him the match.

The Filipino icon, who lost the fight in a 12-round decision, revealed after the bout that he had suffered a torn rotator cuff in his right shoulder during training. He will undergo surgery this week and could be out of action for up to a year.

Pacquiao, 36, has also been hit with a lawsuit from two Nevada residents seeking damages for anyone who paid to watch the fight.

According to BBC News, Pacquiao's camp claims that they had notified the United States Anti-Doping Agency of the injury and had received approval for him to use Toradol, a non-steroid anti-inflammatory as treatment, on the night of the fight.

However, the Nevada Athletic Commission stopped the treatment shortly before the fight, claiming that they were not told about his shoulder issue.