Actually, that's the sad inaccurate reality of the ATP rankings.
Basically, rankings are determined by the points accumulated from
tournaments each player chooses to play without taking into
account the surface on which a tournament is played on.
Hence, it can be easily concluded a claycourt specialist actually
has a massive edge over a grasscourt specialist simply because
there're more claycourt tournaments than grasscourt ones on the ATP
calendar (and therefore, easier for the claycourt specialist to
chalk up points).
Roddick has a proven pedigree on both grass and hardcourts which
explains his formidable ranking. That said, he's hardly competent
on clay, but I don't suppose the French Open organisers could
ignore his overall ATP ranking.
On a sidenote, I think Davydenko's been dissapointing lately - then
again, most Russians are unreliably inconsistent anyway...
