A second time around, however, would see Pacquiao get the better of the undefeated welterweight champion, his trainer, Freddie Roach, said.
"Manny would do much better in a rematch, if the shoulder gets better," Roach told the Boxing News. "We were doing well until the shoulder went in the fourth round, and we had a tough time after that. I do think we can beat Mayweather, 100%."
Pacquiao was dealing with a right shoulder injury going into his bout with Mayweather. The injury occurred during a previous sparring session and required surgery after his loss in the ring to the champion. Pacquiao is not expected back in the ring until 2016.
Mayweather (48-0, 26 knockouts) is set to face Andre Berto (33-3, 23 KOs) on Sept. 12 in what is being billed as his final fight, which would make it difficult to get Pacquiao back in the ring with him.
"I don't know where Mayweather's going right now. I don't think he'll stop at 49 fights; I think he'll fight to 50. I'm hoping that he promotes himself. Maybe if he does, he can make more money," Roach said.