#2 Arsenal sat deep to break on the counter
Arsenal were resolute at the back but the one thing you ought not to do against this Manchester United side is sitting back and soaking up the pressure. Manchester United players thrive when they're afforded time on the ball and space in the centre of the park and there was plenty for them to exploit at times.
Though Nelson and Bellerin offered attacking outlets, they couldn't get going as frequently as Arsenal would have liked. When Arsenal finally went on to cause problems by breaking United's play, they were rewarded with a goal, scored by former United player Henrikh Mkhitaryan.
In the last quarter of an hour, Arsenal were pegged further back into their own half and this ended in them not creating anything of note in that period. They also conceded in stoppage time and failed to put the icing on the cake on an inspired performance from the youngsters.