Afaik head to head stats would the one to be used as tie breaker if points are equal at the end of the group stage . If PSG is to fail tomorrow means that both PSG and MU has 9 points, but PSG is leading head to head by 2-1 and 1-3 means that PSG will stay on 2nd position no matter what is the result of their match against Basaksehir. Correct me if I'm wrong.