The Philippines superstar had beaten Marquez twice and drawn a third bout before a well placed upper cut from the Mexican knocked him out in the sixth round of their fourth meeting.
Pacquiao has won all three of his fights since then, downing Brandon Rios, Timothy Bradley and Chris Algieri. However, Mayweather Sr believes that Pacquiao still carries the scars of his defeat to Marquez and has asserted that he will get knocked out once more when he faces Floyd Mayweather Jr this weekend.
"Once you get hit like Pacquiao got hit by Marquez, it won't take too many more punches until it happens again," said Mayweather Sr.
"This fight is already won. Trust me."
Not surprisingly, Pacquaio's long-time trainer, Freddy Roach, feels differently.
"Manny knows that knockouts are a part of boxing," said Roach."If you don't want to get knocked out, go do something else.
"It was a bad knockout against Marquez, he was down for a long time. I was worried but when we got back in the gym there was no change, he wasn't gun shy.
"But Floyd has put on extra muscle and can punch when he wants to. So I hope he chooses to come out in the early rounds and tries to knock us out.
"Floyd will be looking to land that big overhand right, which was kind of a sucker shot, a shot fighters like Manny shouldn't be hit with."