It looked to me like he was the fresher, sharper player at that point of the match and then Novak just went into another gear. Unreal.
Murray was better pretty much that whole set, and still lost it. That's just what Novak does though. He chugs along all ho-hum, gives you a false sense of security, and out of nowhere hits you right in the mouth. He's a freak.
On that Novak serve that was out but called in, they shoulda called it out just based on the fact that he had 2 straight double faults. Bad break for Murray.