He's been in trouble off of clay since 2009 (his first long term injury break). Before the 2009 injury break, it had looked like he might even start to dominate hard court. He won Canada 2008, Olympics 2008, AO 2009, IW 2009, and I was "wow, here comes the hard court beast, clay specialist my foot!!!" Then his body fell apart. Then it took him until USO 2010 to win another title on hard and that was after a spectacular serve transformation that he couldn't maintain afterwards. His Tokyo 2010 win was vs a pretty weak field (Monfils in the final). After that, he often seemed to come close but somehow fell short at the finish line, which was damn frustrating: against Fed at WTF 2010, against Djoko throughout 2011 and at AO 2012 (so often it must have been a true psy nightmare for poor Rafa) and vs Murray in Tokyo 2011. And that was in the best case scenario: when it was actually close, because he also had some counter perf vs lesser players. OK, why am I telling all this? Because I don't think that all those struggles had much impact on his clay perf and confidence. He still won RG in 2011, he still kicked ass on clay in 2012. I don't think anything will change in 2013 (unless his knees refuse to recover and he has to call it a day).