Williamson lacks quite a bit of pace. It'll be interesting to see how he copes in the PL, because he generally is a very good CB from what we've seen. He's brave, calm and sensible....good reader of the game as well.
Coloccini isn't the quickest either (good reader of the game though) so it will be interesting to see how we do when we come up against players like Torres, Rooney and Drogba.