Hello there hercules, yellowball, prattennis_1, jeffrx. Welcome to tennis4you.
In my opinion Nadal is pretty strong mentally, and always comes up with something special, and finds a way to win a match even though if he is not playing his best tennis. He makes the game very physical, and it plays to his advantage. His game is improving, but some top players do have the weapons to cause damage against him. Thats why we see many 4 pr 5 setters in grand slams, tight sets, but Rafa with his never say die attitude some how manages to win.