If you base Floyd beating Golovkin on the Jacobs fight - a 6'1 quick middleweight with a reach advantage that fights nothing like Floyd - then equally you have to consider Floyd "losing" to Castilo.

So based on how easily a 5'7, "slow" lightweight was able to pressure Floyd then a 5'11 middleweight with a longer reach, fantastic jab, bone crunching power and a granite strong bonce would absolutely kill him.

Yeah.. I wonder why Floyd never attempted winning a middleweight title.