Mayweather vs Golovkin? To Floyd Mayweather Sr, it's an absurd idea, with simply too much actual size difference even if Gennady Golovkin were able to make a 154-pound limit for the possible fight.
Here's what Floyd said in the video from Jeff Mayweather's ProBoxingInsider.com:
"I would say something about this GGG. GGG, hey, if GGG can make weight, that would be different, but -- no, no, we not fixin' to fight no damn giant. I'm gonna tell you like this right here. He comes down, he be at 154, by the time he eats and fight that night, maybe 180, you just don't know, man. People can eat up stuff, man, and hey. He don't need to fight nobody like that, man. Now they say that Floyd won't beat him, but I'm just telling you because, the guy is probably just so big and strong, man. Floyd probably, all he would be doing is, he'd take a lot of punches. He'd come in, Floyd would run the stuff off of him. But the whole thing is, it'd be a struggle, but Floyd probably could beat him. I can't say that he can't beat him."
On my end, I think Mayweather Sr is right that it's just too much to ask of Mayweather to fight a destructive middleweight who would have an enormous size advantage on him. Mayweather has fought three fights at 154 pounds in his career, with Oscar De La Hoya, Miguel Cotto, and Canelo Alvarez. He's 3-0 in those fights, but it was also clear that he was really pushing his physical limits.
While challenge and risk are great to see in boxing, weight classes exist for a reason, and Mayweather is not a junior middleweight. That he's had success at that weight against top fighters is a testament to his skill, but it's really unfair to ask Mayweather to take that type of risks. Take risks against good fighters in his weight class, yes, but out of it? That's another story.