He's good, but I don't think he's world class. If Chelsea are serious about going for the Premiership and the Champions League then they should be looking at the players a level above him.
you are saying they should buy only stars?
Don't agree with that!!
Kezman is very good but can get better.
Mourinho did that with Nuno Valente, Paulo Ferreira (that he bought) and Maniche, Ricardo carvalho, Helder Postiga improved their game a lot.