Andy is only favourite on paper because of his past history - 2 times slams champion etc. but his current form is another matter as he's quite vulnerable to lose to basically anybody.
Anyway, just finished watching a bit of Nadal/Dolgo match. From what I saw, Nadal didn't play very smart tennis against a very unpredictable Dolgo. He gave him a lot of short balls for a start and Doglo was all over those balls. And also, he let Dolgo play well inside the baseline a lot and that pretty much kept Nadal constantly on the run. He was taken out of his comfort zone a lot and for that reason, he wasn't allowed to do what he usually does - dictate the points with this forehand and put as much topspin as possible.