He did do it in big games for United. Unfortunately for him though, whilst he is the second best player in the world, the first best player is streets ahead. Leo Messi is simply amazing, and he keeps getting better. He needs to do it at the World Cup to end up ranking alongside Maradonna, but he doesn't necessarily have to do it in South Africa. He is only 22, so you could easily be looking at two, if not three, more world cups after this one.
Also.... Xavi. Wow. Best midfielder on the planet, he is phenomenal.