Nadal's record against Federer is 22-10. If you take out the 6or7 times Federer lost to him in the French open, their record is closer. On hard courts it's about even.
Although Nadal has beaten Federer the last 5 times they played, the law of averages would suggest Federer is due for a win.
If Federer can prevent his forehand form going "awol" and plays like he did in the first 2 sets against Murray, he might have a chance.
Its been a while since Roger got the better of Rafa....
I would love the Fed to get one over his arch rival....i just don't see it happening. Nadal is much more fitter, and that will be Rogers biggest hurdle to overcome.