Nobody in sight if it wouldn't be Djokovic. Djokovic is not having a great claycourt season, but if he can somehow refind 2011 form, he's your man.
Nadal will always have a matchup issue with Djokovic like Fed has with Nadal. However, whilst Federer and Nadal are close to each other in consistency, Nadal is just been more consistent over the course of his career than Djokovic. I think the matchup still favours Djokovic a ton though. If Fed and Nadal and Djokovic play equally well (measured against the field for instance), Nadal will always beat Federer, Federer will always beat Novak, Novak will always beat Rafa.