Marquez the toughest fighter on PBF resume?

[Micka]

^^ no doubt

[Pugilistic™]

Marquez would be tough for Mayweather if both fighters were naturally the same size, unforenately they ain't. At this stage of their careers Marquez is a small lightweight and Mayweather is a welterweight. Marquez is simply too small to cause Mayweather any problems.

The toughest fight in Mayweather's career has to be the first Castillo fight.