you should go back then and watch the film of Mahrez last season to this, watch HIS actions when he receives the ball, last season he was on the front foot, decisive and offensively aggressive.
this season he waits, is indecisive and lacking of offensive aggression, frankly, he has always been poor defensively but made up for it going forward, this season he hasn't contributed, no one expected him to match last season but he should have still done a damn site more than he has and he's been allowed to get away with it