A lot will depend too on how his opponent plays. Other players get nervous and tight as well, although I do agree that Andy still seems to have problems with his concentration which is something Djoko, Fed and Nadal don't have.
Yeah for sure.... Andy has struggled in the past against Ferrer....and Haas beat Djoko who is technically similar player to Andy...of course there is Berdych too...who he has a tight h2h with. No Nadal, Fed or Djoko counts for little if he doesn't get past those guys. Andy can raise his game much higher than what he has produced thus far...so Im sure any opponent will have that in mind too.
His lack of concentration is ridiculous sometimes...and really sets him back. Today he was distracted by a ref time wasting warning ....and a Aeroplane flying over his head for goodness sake. Come on Andy stop that!.... pretty please ...lol