An interesting thing I heard in an on-court interview Jim Courier had with Dolgopolov just after he beat Soderling. I think I heard that his father coached Medvedev, and as a young kid Dolgopolov had a hit with some of the other players at the French Open a few times. Courier was incredibly impressed with him then and apparently saw him as a future star. Courier asked him if he remembered who he was, and Dolgopolov replied that he did, but not the first time as he was only 3 years old at that stage, but did a few years later. If that's true, then the kid must have been really good from an early stage, and perhaps the exposure to the game from early in his life was what caused that.
Anyway, Federer beat Wawrinka, Djokovic beat Berdych, Li Na beat Petkovic and Wozniacki fought back to beat Schiavone.