Only thing keeping him on is his recovery work. He's very useful stopping counters, which has been our weakness in midfield. Much better than Xhaka who can only really defend facing forward.
Too bad the rest of his game is so bad, because I don't think Vieira or Trossard can do what he does on the defensive side.
Arteta may be partially at fault, here. He's got him doing hold up work in the midfield, so he's laying it off backwards when there are runners ahead of him. If he could only find a way to get him facing forward more when receiving, maybe we'd see more of his playmaking or running with the ball. His defensive strengths and attacking weaknesses seem related to some extent.