I think given time Koeman's capable of coaching us in to a better defensive shape.
That could take a while though. We've got a midweek game every week until the October international break. If we get past Sunderland in the cup, that's going to extend at a minimum into November.
Will he actually have the opportunity in training to get the message across to the players? Especially if we're also trying to fix an attack and concentrate on the next opponents too? Even with the easier games coming up, this is something that could drag on a while longer yet.
The same problems will obviously extend to any new managers that come in too, so it goes both ways. Just something that I've been mulling over.