Haas has won Djokovic recently in three sets (in Halle). That means he knows how to play with Djokovic, his weak and strong sides. Sure, Novak is top-class player and shows good tennis at this tournament, he has won Sela easily, but I should note Djokovic always plays great with opponents who is really weaker (as Sela was) and there will be other story in match with Haas. Tommy has shown that he is mentally strong, won Cilic in very tight match, that fact shows he is ready to fight and even ready to reach semi-final (handicap is more safer).