Apart from say the obvious ones like Hagler or Monzon, which Middleweight s that came after Sugar Ray Robinson, could potentially give him hell?
If we're counting in SMW in this, then Andre Ward. Roughly the same size and both know how to fight in the trenches when the going gets tough.
I’m confident that Robinson would outbox Bernard Hopkins but I’m wondering if Bernard might give him a decent match. B-Hop was crafty, highly skilled, durable and always in good shape.
