well, it is not so easy, to improve on this high level of tennis (TOP 30 already high level is) I dont know, every player has some own best, and Klizan is maybe reaching it. His serve is very very weak in comparison of TOP 40 players. Yes, he has a game, but it is really exhausting to play every service rally long. I dont see that Klizan will have so big serve, to compete with TOP 10 guys often... Yes, when Klizan has day, and TOP 20 player doesnt, Martin can win.
But you know, everything is in stars, I m huge fan of Martin, I saw lot of matches from him, but this is my opinion, Hope it will be wrong in a 2 years