Manny is the kind of a guy who would have only had a chance against Mayweather at his peak, though. He needed to have all his hunger, speed, ferocity, reflexes, in order to overcome the skill gap.
A rich, slowed down Pacquiao who had already been iced by Marquez, just wasn't going to present Mayweather with the kind of problems that an absolute peak Pacquiao could have.
None of that means that Floyd couldn't have overcome Pacquiao while he was at his own peak, though. It just would've been more interesting.
It's a shame that the business side of boxing interfered with that match-up.