I'd say serving first in a set is a HUGE advantage. Djokovic was BACK in the game in the 4th, Nadal had no break, one double fault (Thanks to that crowd) and goes away the match. Djokovic was immensely frustrated to say the least, the moment his second serve was called OUT, he thumbs-uped the crowd from where those noises were coming.
The next target of ATP should be sound proof courts. They should really do it now.
I won't say Djoker played bad, but he was not at his best at all. If today it's Djokovic v/s Nadal again, I'd still go with Djokovic. Really bad luck.