Anybody can win any given fight. What ifs are coulda shoulda wouldas. If size and weight didn't matter then we'd have featherweight fighting super heavyweights. of course size matters. It doesn't guarantee a win every fight but it does give you advantages. Rocky ko'd joe louis when louis outweighed him by 20 some pounds. Size and greatness didn't matter in that fight, but it does in a lot of others.