Yeah big serve, not allowing Djok to get into the 24 point rally stuff.
Playing less physical and really hurting his second serve. You must get into 'serious' points. That is he has pressure on him to win that point.
It takes someone with a great serve and the ability to hurt the second serve to take Djok deep.
Fed does this, Isner is all about this and Roddick could do this.
Nadal does it a whole different way - he mirrors Djok and attempts to outgrind him.
Murray has the serve, but lacks the hard return shot (but gets to everything also) and begins to play grind out tennis. I'd say a bit of a hybrid. The fact he was hitting the ball harder at the USO was the difference.