Henderson won the 1st round in their fight. The only one that I think would give Silva a good challenge in that entire division is Chael Sonnen and he's not even officially in the UFC yet, that I know of.
And then he got smoked in the second round.
Chael Sonnen would get smoked if he were to face Silva. Standing, Silva takes it, and if Chael gets him down, Silva will just sub him. Silva's guard is active and Chael really fights like a dumbass most of the time.
Odd that you think Chael would be the only good challenge. I mean, dudes like Maia, Palhares, Almeida and Marquardt in a rematch would be better opponents.