Hard to imagine a welter lasting long with GGG. Maybe Hearns if he works his jab and doesn't slow down. Ray Leonard and Floyd may have been able to use perpetual, non-stop movement for the decision. The truth is, GGG is just too damn big, strong, and good at cutting off the ring. The guy that beats him will be a bigger guy with solid skills, good movement, and elite level durability/chin. An extremely fast fighter in great shape may pull the upset off, but that will be a tall order and luck will be required.