I honestly think there has never been a player with Novak's ability and possibly there never will be. He's so fit and hungry and you can see just how determined he is to own the sport. He is 31 but it's more like 24 and I can't see a player who can challenge him, not even Nadal on clay. On the other surfaces he is a clear favourite and nothing other than Novak himself can stop him. How many slams will he get? Would you bet against another 10 slams? I wouldn't. There simply is no other player out there who can challenge him. It would not suprise me if he finished his career with 25 slams and more.