By Edward Chaykovsky

Trainer Floyd Mayweather Sr. is still convinced that eight division former champion Manny Pacquiao was taking performance enhancing drugs a few years. The past PED claims by Mayweather Sr. had forced Pacquiao's hand in filing a defamation lawsuit.

Mayweather Sr. believes Pacquiao was taking something during his victories against Oscar De La Hoya, Ricky Hatton, Miguel Cotto, Joshua Clottey and Antonio Margarito.

For his last fight, against Brandon Rios, Pacquiao took part in a random drug testing protocol, and he tested clean in every test. According to Mayweather Sr., that further proves his past theory, because he says Pacquiao has been unable to score a knockout since 2009 and hit Rios with everything possible but could never seriously hurt him.

If a mega-fight eventually gets made with Floyd Mayweather Jr., his father predicts a one-sided beating against the "clean" Pacquiao. 

"I’m just telling you right now that it’s very, very good that whatever he was doing before that he was getting all these outstanding knockouts, hitting everybody, fighting middleweights and all that. It just shows you right here, he had a guy he could hit all night long and the guy couldn’t even fight, plus the guy had drugs in him," Mayweather Sr. told On The Ropes Boxing Radio.

"[Rios] couldn’t fight at all and Pacquiao still didn’t get him out, it wasn’t meant for Pacquiao to get him out because like you said, Pacquiao came back clean this time. If he was clean all the other times, he wouldn’t be where he’s at today, he wouldn’t be talking about fighting my son right now if he hadn’t been doing what he was doing back a while ago. Now if he wants to fight my son clean like he is, he’s gonna get his ass whooped, simple."