This would be a really cool fight at 154.
I think we can discount Golovkin's jab. It's too slow to deal with Floyd's masterful skillset.
And Floyd would obviously have to run around and dodge.
That said, if you look at all the guys that have fought Floyd, only a few have pressured him. Cotto did, but Cotto wasn't nearly as strong as Golovkin, nor did he go to the body nearly as much, nor could he take the punches that Golovkin has shown he can take.
Castillo was aggressive and went to the body and almost won.
That's really the only way someone beats him. You need to get inside, take punches well, and go to the body with big shots. That should be able to win rounds and put you in place for a decision win (KO is always a possibility, but doubtful at 140-154 vs Floyd).
Golovkin is capable of doing all that.
That doesn't mean I think Golovkin is >50% to win, but he sure as hell seems to have a solid double digit chance, something few others have at 140-154.
Also, gosh, do some people around here just go around posting Floyd hate every day? I guess that's the result of a very good fighter playing the villain role for years. He's beaten better fighters than Manny or Cotto, and while it's ridiculous the Manny fight never got made, the advantage of being the top fighter is that you can say "I deserve my market value" and not have to sink down to take 50-50 against a fighter who is not worth as much in terms of PPV money.
People used to say Floyd was ducking Cotto, but as soon as the money was right, he jumped on it, beat him clearly in 8 rounds, and probably took 1-2 others if we're being fair, and then the crowd split between "Cotto was over the hill (even though by all evidence he was still prime, and far younger than Floyd)" and "Cotto almost beat him."
You don't have to like the best fighter in the game, but you should at least respect that he's the best and he's beaten the best fighters out of anyone at 140-154. Hatton's first loss, Corrales first loss, cakewalk against Marquez (who has fought close fights against some of the best fighters over the years, don't even need to count Manny knockout, he was fighting a close fight though losing against Manny prior to that and Floyd walked right over Marquez), cakewalk against Canelo (who handily beat Trout, a top 154 fighter and walked through anyone else he's fought, Lopez, etc.). Not to mention all the top 3-4 contenders in the 140-147 he's fought over the years. All these Guererro type guys "suck" after Floyd beats them (according to haters). Ironic.
The only top fighters people should be legitimately hating on as being so overrated it's not even funny are guys like Chavez Jr.