Stan's had a good amount of match practice on clay already. He played in Buenos Aires (beating Almagro in the semis and losing to Ferrer in 3 sets in the final), Acapulco (lost in his first match to Fognini), and Casablanca (lost to Robredo in the semis after winning the first set 6-1). He plays well on clay and seems comfortable on the surface.
That's what worries me a little, but I felt that today Andy, for the first time, looked as though he belonged on clay. Comfortable, relaxed and moving very well.
I've gone for Andy in 3, but, like all their matches, apart from the Olympics, I'm expecting it to be a nail-biting rollercoaster ride.