The Slams are the factor when talking about historical significance. Djokovic still looks like he's in the mood to win many titles as opposed to doing what Nadal and Federer do which is to save their best for the Slams. Since both Nadal and Federer are playing for the sake of history and legacy and both want to keep adding to their Slam tally while taking it easier in the Masters tournies, when will Djokovic begin to go this route? To use the Masters as a way to improve form and then going all-out at the Slams? If he's at 4 Slams, it's very very likely that people will really begin to take notice of where he stands amongst the greats if he can get into the range of 6 Slams. I believe it was at 6 Slams when people began to really start discussing Nadal's legacy on the boards and how much more he could achieve. If Djokovic gets Roland Garros in 2012, will it be time to start talking about his standing amongst the best players throughout history (Agassi, Lendl, McEnroe)?