I guess being in grass on a two set format is not going to help Nadal much... If it were a 5 set format would be a different story...
Djokovic, Federer or Murray are the ones that come to mind....
I think Murray will come with extra determination on the Olympics at home, and that can definitely be a plus aside from the fact that he is eager to have a major title on his shelf. On the other side, I am betting Djokovic wants to prove that he is still the dominant player on tour and will not let his guard down.
To tough to call...