there are probably hundreds of undefeated fighters right now, but what makes you number one pound 4 pound is the quality of fighter you faced, are they bigger, stronger? must beat and dominate someone higher than your natural weight on a regular basis, that will prove a fighter is beyond numbers
marquez is probably the best fighter in the 135 pound division, but at 144, mayweather will have tremendous advantage in height, reach, and weight. PBF should fight someone at least near his size.