Wow, how insightful from Bodo, the nr.2 clay player for years can beat the nr.1
Makes me wonder why I didn't become a sports journalist.
Now Fed has several things going on for him on clay:
-superb movement.
-more time to hit his shots.
-great dropshots.
Unfortunately some ugly bits stick out:
-slow court means that he can't hit past the good defenders on this surface(and this was a major problem for him on the slow HC this year).
-guys that play with lots of spin can abuse his BH even more(again, a big problem for Fed).
-serve doesn't matter as much(though Fed hasn't exactly been an ace machine in 2011) so he will have to play baseline all the time.
In short, on clay Fed will be forced by the naturally good clay players to play a game of atrition, to play baseline all day long and will certainly get his backhand tested A LOT. He is a great clay player but the odds certainly don't favour him against Nadal on this surface.