I don't think it's raw athleticism, but using that athleticism in a techinically effecient way that benefits tennis. I'm sure there are kids playing division one tennis who could outsprint every top 10 player, but tennis isn't about that.
And mental consistency is a given, where the Feds and Nadals are just above everyone else.
And mental consistency is a given, where the Feds and Nadals are just above everyone else.