Guerrero is definitely a very skilled fighter (although we didn't see too much of that tonight.) And he's got an amazing chin. But what I don't get is how you can come up from lightweight to welterweight and be able to bully guys like Berto around without some help. You've basically got to assume that everybody at the top level in boxing is taking something until it's proved otherwise. Other than Donaire, who is the only top fighter to agree to year-round random testing I wouldn't put any money on any of these guys being clean.