nadal is his own man. he believes in doing things his way.
if I can narrow this down to just one thing, I would say its the drop in fitness.
he has let his fitness take a hit this year. seems like he decided to take a bit of mental and physical vacation since the last u.s. open. and he has never really recovered from that.
and then the back injury at the worst possible time hit.
he is just not as fast and as strong as he used to be. for that reason they are able to get to his shots and he is not able to get to their shots.
by giving them 1/2 the court and by playing mostly forehands, the element of surprise does not exist at all.
you can do only 2 things with that forehand hit from his backhand corner: you can go inside out or you can go down the line. his positioning gives it away. they know where he is going most of the time.
not much time left. if anybody can fix some of this, he can. all he has to do is bag rome and RG and a lot of these issues will go away temporarily anyway.