Putting game mechanics aside, what impresses me with this guy the most is how he carries himself on court. A lot has been said about how temperamental he was when younger. But now he just gives off this message to his opponent like "Do whatever you have to do, take your time, I'm just gonna play my game". Rarely you will see him argue with the umpire. When he hits a shot, thinks it was a good shot but gets called otherwise, he just gives it a look and carries on.