Otamendi was the right sided defender, he should have been the one in the massive gap between Sagna and Kolarov/Mangala (who rightly went over to help him out)that Morata run into before taking the shot. That is exactly where Otamendi should have been.
If he was in position he would have swept up the ball coming off Kolarov or he would have been able to tackle Morata/block the shot.
So are you saying Otamendi should just let Morata run into space untracked?