Yes that plays a part but mental lapses don't help either. He has had them lots of times in key matches that have cost him wins. Australian Open Final this year springs to mind for a start, brain freeze in 2012 final when he led Roger in the final then the roof closed and he fell apart and then we had a semi at Wimbledon a few years back when he was leading Nadal and missed a sitter and he capitulated. Probably lots more as well. Talent-wise he is right up there but mentally he isn't in the same league as Federer, Nadal and Djokovic.