Re: How can a player be "tired" after 2 days rest?
Well, I think you made a wrong comparaison with cycling and running.
I will just answer on one thing : in tennis, you can be tired physically of course, but also mentally. You need to be sooo focus at the ATP level, on each point, you have to come with a plan, you have to be ready to adapt it, handle the pressure in the decisive moment, accept the frustration... tennis is such an exhausted sport in the mental department. A 5 sets' match takes you a lot of energy in the mental department because tennis in more emotional than others sports.