Cain is obviously on stamina boosters. This dude is 245 lbs. and throws around other 250 + lbs. guys for 25 minutes and never gets tired. he has EPO written all over him.
I think Diaz bros, Florian and Roy are the only clean fighters. Maybe a good amount of the women. Any consistently physically dominant monster has to be on PEDs cause a clean dude is just not doing that to guys on gear, and it's clear that that's the majority of MMA fighters (one of the reasons I feel GSP is one of the biggest liars/hypocrites ever for insinuating he's one of the clean guys).