What's happening with Novak Djokovic?

Novak's form has dropped over the last few months, and he's not his usual brutal self on court. I'm wondering if it's because of the Rod incident at the US Open, when he seemed to be really affected emotionally by the consequences of his post-match statements - he was very withdrawn in the semi-final match against Federer, not pumping himself up and making the usual grunts on his ground strokes. He was the same in his match against Tsonga today; the usual intensity was missing and he accepted his loss so casually. Where is the Novak that played the super aggressive tennis that beat Nadal in Cincinnati - he was menacing on court that day. Do you think he just needs a new coach to further inspire him because he's outgrown the current one? I think Novak is great for the game, and I hope he returns to his old form soon, or Murray could overtake him by early next year.