It was one of those ‘what might have been?’ moments. A moment which, had Lady Luck been shining down on Manchester United that day, could have sent their season moving in a very different direction. When title-chasing Arsenal arrive at Old Trafford on Sunday, they will take on a Red Devils side lurching from crisis to catastrophe. A team who have already suffered a record number of Premier League defeats, could finish outside the top-seven for the first-time, and who’s manager – the increasingly embattled Erik ten Hag – appears to have aged decades in a matter of months. But where would Manche…