What's missing in Nadal that he can't dominate the way Federer did?

Whats missing is the competition (or the lack of) that federer enjoyed. Other than Nadal on clay courts which great player did federer have to contend with? Rod? While Nadal has to deal with Federer himself, Novak, Delpo and Murray also partly. Had Nadal and Djokovic been born around the same time Federer was born, I doubt federer would have more than 10 slams.