Maidana's pressure remained intense throughout the fight as he never stopped moving forward and trying to push Mayweather against the ropes. But even though he did, Mayweather countered with quick right hands. In the third round, Mayweather also opened up with a series of body punches. Referee Tony Weeks also warned Maidana for hitting behind the head in the third round.
As aggressive as Maidana was, Mayweather stood in the pocket and was sharp with his right hand, but Maidana would not stop coming at him and winging overhand rights. He cut Mayweather over the right eye in the fourth round, a rarity in Mayweather's career.
"That came from a head-butt and I couldn't see for two rounds after the head-butt, but that's what champions do -- they survive and they adjust," Mayweather said. "True champions adjust to anything. He's a champion, I'm a champion and we did what we did in there tonight.
"I had a great cutman in Rafael Garcia and he stopped the bleeding immediately and after I could see again, it didn't bother me. [Maidana] is a tough competitor."
The action continued in a tremendous action- and tension-filled fight with an electric atmosphere in an arena that would alternately fill with chants of "Argentina! Argentina!" and then "USA! USA! USA!"
No matter what Mayweather, 37, of Las Vegas, would do, Maidana would not go away. He was swinging heavy punches and taking everything Mayweather threw at him. And Mayweather, who earned at least $32 million, landed a lot of clean right hands and left hooks.
Maidana, 30, who made at least $1.5 million plus television revenue from Argentina and upside on the pay-per-view profits, was so aggressive that during the 11th round, he nearly tackled Mayweather out of the ring.
"I think it was a very, very exciting fight. Maidana came to fight. We all knew Maidana would come to fight and he did. He always does," Golden Boy Promotions chief executive Richard Schaefer said. "He was not intimidated by Floyd. Even though Floyd landed some good shots it didn't seem to hurt Maidana at all. He kept coming and he wasn't going to give up."
With the win, Mayweather, who has now won 10 alphabet titles in five weight classes, became the first fighter in boxing history to simultaneously unify alphabet belts in two weight classes -- welterweight and junior middleweight -- although the organizations' rules do not allow fighters to hold belts in multiple divisions. But they have made an exception for Mayweather, who brings them big money with each of his bouts.
With no obvious September opponent for Mayweather to face in the fourth fight of his six-fight, $200 million-plus contract he signed last year with Showtime/CBS -- we've already been down the Manny Pacquiao road too many times to be fooled again -- the prospect of a rematch with Maidana seemed quite real.
"I'll sit down with the teams and see if that's what gonna be next," Schaefer said, who added that he liked the idea of a sequel.
Maidana, of course, felt robbed and wants to do it again.
"Yes, I did go after him. He's a difficult fighter but I won," he said. "I would have to give him a rematch because I won the fight [because Mayweather had a rematch clause in his contract]. Yes, I would give him a rematch."
Ultimately, the decision will rest with Mayweather, who talked about possible retirement in the days leading up to the fight. But he didn't sound that way after the toughest fight of his life.
"If the fans want to see it again," he said, "let's do it again."