If Djokovic goes down, I reckon it'd be in a tough match. Even though he lost in straight sets to Federer at the US Open, he was in every one of the three sets, Federer just won the key points.
Btw, I reckon there should be a new tennis rule. Everytime James Blake makes the quarter final of a grand slam, he gets to be replaced by Marat Safin. So Blake can play the early rounds where Safin normally loses because he doesn't care, and then Safin is subbed in from the quarters onwards.
That way we don't have to see Blake in the last few rounds wasting our time