hmmm... it is true that tomorrow's match does not defines what happens at RG, however, to say that it has no bearing on it is too much for me.
To begin with, if Nadal wins tomorrow (something I do not think will happen), must people would say RG is already decided (and, honestly, it would be hard to think otherwise).
If, say, Djokovic wins 6x4 7x5, then ok, let's wait for the next rounds, but if he thrashes Nadal like 6x1 6x1 (and, I am sorry, by current form this is not impossible, and Djokovic would love to do just that), considering still the confidence issues that are there for everyone to see, how can we say that this would not have an effect for RG? Sure as hell that it would...
So, in two out of three scenarios this match could arguably have some measurable effect on RG, and I would guess those two guys are pretty aware of that, and that this will be visible on court tomorrow.