Mustafi is poor, someone said he could have 30 good games and 1 bad game and he would get crucified. Well that hypothetical situation would NEVER occur, he can't go a single game without making a bad mistake.
Own goals, penalties, charging past the halfway line diving in to tackles and missing - exposing the team to a counter attack. This is Mustafi's MO, he is a nightmare and if I ever see him play again for Arsenal, a piece of my heart will die.