As usual, he found a way to win.
Mayweather used his speed and accuracy Saturday night to take a unanimous decision over a game Cotto in a bruising bout to win a piece of the 154-pound title. But it wasn't easy, as Cotto landed some hard punches and kept attacking all the way to the final bell.
''You're a hell of a champion,'' Mayweather told Cotto in the ring afterward. ''You're the toughest guy I ever fought.''
Mayweather dominated late, rocking Cotto in the 12th round to pull out a win and remain unbeaten in 43 fights. Unlike most of his fights, though, Mayweather got his nose bloodied and engaged in some bruising exchanges he usually likes to avoid.
Two judges scored the fight 117-111 and the third had it 118-110. The Associated Press had Mayweather winning 116-112.
Fighting just a few weeks before he enters a county jail to serve a three-month sentence for domestic abuse, Mayweather found himself in a tough fight against a game opponent who never stopped moving forward. But he was faster and more accurate than Cotto and seemed to wear him down in the final rounds.
In the last round, Mayweather landed his best punch of the night, a left uppercut that seemed to hurt Cotto. He followed that with several flurries to the head to wrap up a decision that until the later rounds had been in doubt.
The decision was roundly booed by the crowd at the MGM Grand arena, which cheered wildly every time Cotto landed a punch.
''He's a tough competitor,'' Mayweather said. ''He came to fight, he didn't just come to survive. I dug down and fought him back.''
Cotto was never down, though he seemed hurt several times during the fight, particularly in the 12th round.
''The judges said I lost the fight, I can't do anything else,'' Cotto said. ''I'm happy with my fight and performance and so is my family. I can't ask for anything else.''
Mayweather, who was guaranteed $32 million, was forced to fight every minute of all 12 rounds against the Puerto Rican champion. He did it after weighing in at 151 pounds, the heaviest he has ever been for a fight.