He also hasn't won a single match at the French Open yet (in his entire career), and he's down a set in his first round as we speak so that trend might continue. It's odd, because you'd think his fantastic rallying abilities would suit the surface decently. He has managed to beat Novak on this surface, though.
I think it comes down to (1) His movement isn't the most natural on this surface, he's a big guy after all! and (2) He's got a big first serve which earns him free points on the other surfaces but not so much here.