good point lady TT.
I know my own situation on the court when I used to play and compete: you sometimes tend to play as well as you need to and also in accordance with how your opponent is playing.
you are more motivated against more talented players and you tend to play better.
and in this case there is that matter of energy and health conservation also. nadal or anybody else cant really afford an injury or too much expenditure of physical and mental capital this early on in a slam.