I was thinking about this during the Barcelona final and I´m not sure. Of course, there are more players who could beat Nadal in a given day but I think these two are the strongest after Nadal. Federer and Cañas play totally different styles but Nadal prevailed over both so far with a similar score in their last meetings. I´m not sure if Federer would be confident against Nadal on clay given his 0-5 record. Also, best of 5 sets matches are supposed to favour Nadal but Federer is world no. 1 and deserves respect. Cañas will probably be seeded in the FO and depending of the draw he could even meet Federer or Nadal in 3rd round (if he is seeded in the 17-32 frame). He is really consistent and tough. Not only his defensive game is amazing but he can also hit some winners with his forehand. If he could beat Federer twice on hardcourts, I like his chances to beat Federer on clay but it all depends of the draw. His main problem is that his style is so physically demanding that he could be out of gas in the latest rounds or not at his best. Federer can play brilliant tennis but his consistency in a best of 5 sets match on clay is not the best against extremely consistent players like Nadal and Cañas. Cañas consistency could be compared to Nadal´s but he needs to work too much on every point against someone who barely makes an unforced error like Nadal. But still he is a great fighter and always tough to beat on clay.