If I know one thing about Nadal I know he takes his tennis super seriously. So to think he went into this match unprepared is hard to digest. And also, Nadal might just be focusing much more on RG at this point of his career and the trend shows that he's always vulnerable when he's No. 1.
Beating Nadal at RG is the toughest deal for any player right now so I definitely think the main challenge is there.