Well, Nadal is now in a big form. He plays what he wants. He changes strategies every match and looks brilliant as of fitness form. So, if one of them could feel tiredness - it would be rather Djokovic.
The problems which Nadal showed us in Europe (lose to Youzhny, problems with Andreev) now seems to be gone. I hope it will be an enterteining match but i doubt that Djokovic can win more than one set.
Ps. What exactly happened to Roddick?