He's world class on his day and is probably our most talented player but he needs careful managment to bring the best out of him on a consistent basis. As he's a luxury player, you either build a team around him that suit his strengths and surround him by hardworkers/grafters who would cover up that side of his game that is clearly lacking, or you cash in on him and move on.
Wenger gave him a £350k a week contract and hadn't figured out how to use him. In fact you could argue that Wenger wasted Özil's prime by not supplying him with the type of players that would be compatible with him. Like buying a Ferrari and driving it at 60km/h. Shocking piece of management but nothing new, just one of many examples of his ineptitude.
