He is no super star, never said he was, neither is "average", he does his job, he is the only one defending in the middle, Di Maria (Now injured..) can't defend very well and Gago sucks at defending, so the job falls on Mascherano alone. He is not only playing very well on this World Cup but also he also has personality, I always see him talking to his teammates ordering them to do things right, even insulting them when needed, if you played football in a organized team I'm sure you had one of those guys.
He has spirit, he is hungry for glory, in contrast to many "Super Stars".