Perfect successor of Roger?

Rafeal Nadal is a one of the best players of this generation , of course next only to Roger Federer . He has every quality to become Federer's successor . But the one main concerning thing is his fitness levels . His style of play consumes much of his energy and the amount he plays takes a good toll on him . So I feel that though he has the ability to rightly become Federer's successor , he won't . And mind it , The King's reign is not over yet . He has come back strong yet again to win the World Tour Finals , that too by defeating his arch rival Rafa . Up ahead is a glorious year for the Swiss Maestro . Wishing him all success and Luck :)