here is a list of clay monster`s (nadal) limitations:
1. serve
2. return of serve
3. slice--it is useless
4. volley/net game--he needs to be more confident at being at the net to close/end points.
of these limitations listed, he can probably do without 2 and still dominate. first, he does not really need a big serve. if he could return with consistency and be somewhat aggressive with his return game, it will take a lot of pressure off that weak serve of his.
secondly, if you get to go in on your own terms, you dont have to be able to volley like roger or edberg.
he absolutely must develop a more effective slice and he has to find a way to return better. practice makes perfect.