It is true about the heat and running out of steam in the Slams. But on the other hand, he has won a major before, so I think he can do it again - just not this time. Nadal and Fed are both at full strength. If anyone can do it, he would be one of my top guesses (with Murray.)
His serve windup is definitely abbreviated. He doesn't bring his right elbow and forearm back as much. Not as much arching of the back either, everything more to the right of the body. Is it a better serve?