I think Nadal in a way will do Federer a favor, if he takes Djokovic out here. I am sure Nadal will be a tough opponent for Federer, but Federer has solved his game...the Djokovic game is an unknown, and nobody makes Federer more uncomfortable on serve than Djokovic in big matches.
Do you think that Djokovic, who can lose to Nadal, would've had a better chance against Federer in the eventual final? Honestly, I don't see it happening, if his level is not good enough to beat Rafa on grass, who has been struggling on the surface in the last seven years and who matches bad against Novak, his chances against Roger would be very slim.
Unless you think that Nadal is a tougher match-up for Djokovic than Federer on grass, which I strongly disagree with.