For all the historic good Wenger had done, his stubbornness and shit tactics to address the fact he hasn't had the right personnel at centerback should have been enough to fire him. But Arsenal's board are dickless, so he stays on. Trying to play a back three with Monreal is suicidal and, once again, if there is any sort of injury to Mustafi or Koscielny, there is zero depth to cover even in a normal back four setup.