That's the example I always think of I'm still not sure whether he beats Napoles though (Walker obviously, I'm pretty certain Mayorga would beat up and stop Napoles, within a few rounds) but that's mainly because I haven't seen any footage of him from that time. However; it's clear Napoles would have to be at his cutest to win.
Mickey was, in some respects, a gamma-powered Duran. He was physically -very- strong. Comparison were made between him and the original Joe Walcott in terms of his bullish build and power. He preferred to pressure and brawl but was also known to completely outclass an opponent by playing counter-puncher. He was offensively well-rounded, could be defensively well-rounded, and just as his powers of youth were fading he starting whipping heavyweights before breakfast and without taking off his coat ...sometimes after spending the previous night in a bottle like a Bowery bum. When he fought HW Paul Swiderski the first time in '30, he crawled into the ring. And still won. And when he trained hard, he was a machine. This is a big reason why Greb's half-blind victory over Walker is so damn impressive. Walker was ready for that one. Although for some reason, he chose to train for Schmeling on a golf course. Go figure.
Walker was a terrific body thumper, Napoles was slick as they come but I think Mickey rough him up for the UD