IF Mr. Nadal is not at his best (for whatever reason), and if Robin Soderling is healthy and match fit, he and Mr. Isner are the biggest threat.
Soderling is the only player to defeat Mr. Nadal at Roland Garros. Enough said.
Mr. Isner in 2011 became the only player who has ever taken Mr. Nadal to 5 sets, and Mr. Isner has since improved his play. If he can sustain that improvement and play similarly to his Davis Cup performances and serve well and keep the points short, he can win in less than 5 sets.
Mr. Del Potro has an outside chance.
Mr. Monfils with the match of his life and avoiding Mr. Federer.
Are people still believing in Soderling?
Come on, the 6 straight sets he lost after that match vs. Nadal at RG surely must be a sign, no? It was a fluke, Soderling has less than 0% chance to do it again.