I mean, it's a hard thing to argue but I think the reason he took Quintana out so emphatically in the rematch is because he figured him out. I know, a lot of people say "oh, it was just a lucky shot etc etc" but I honestly believe he figured out Quintana's movement and speed and capitalized early. Plus he's been sparring with Quintana in preparation for this fight, which can't hurt.
Sure.... a world class slick southpaw... you can never count those guys out. If Williams dominates Martinez or even knocks him out he deserves a lot of credit because Martinez is one damn good fighter.