A season in which United have already lost half of their 24 matches in all competitions plumbed new depths as they slumped to a 1-0 loss at home to a Bayern Munich side in third gear.
It condemned Erik ten Hag's side to bottom place in their group with just four points - their lowest total in the Champions League group stage - while the 15 goals they conceded in six games was the most ever by an English side.
For the third time in seven seasons, United have exited at the group stage and this time they do not even have the consolation of the Europa League.
With a daunting trip to Premier League leaders Liverpool at the weekend - a fixture they lost 7-0 last season - the question is are things about to get even worse and how much time does Ten Hag have left to try and turn it around?
"The fans have shown a level of patience, but there's huge disappointment," United's former title-winning defender Steve Bruce told the BBC's Football Daily podcast.
"As we have said many times with United they always look like they're two games away from a crisis.
"Erik ten Hag now has to try and lift the spirits of everyone and the only way you can do that is getting a result (at Liverpool).
"It's a desperate situation they find themselves in."
Ten Hag's first campaign was relatively positive as the former Ajax Amsterdam manager delivered the League Cup, their first trophy fox six years, and put the club back in the Champions League via a third-placed finish in the Premier League.
It earned Ten Hag plenty of credit in the bank but he is using it up fast, even if the fans are largely still behind him.
The truth is, despite 400 million pounds being spent on new signings since Ten Hag took charge, United look like a team lacking a clear vision or direction.
Jaap Stam, a Champions League winner with United in the treble-winning 1999 side, said he fears for fellow Dutchman Ten Hag and says United's recent banning of some media outlets over stories of dressing room rifts just adds to the malaise.
"You need to have peace and quiet," he said.
"You don't want to pay too much attention to other things like players and the press.
"It has to do with your players as well, but he invested a lot of money in players that he brought.
"But are they the right players? My opinion is that they're not."
While imminent investment into the club by Jim Ratcliffe offers some cheer, the immediate concern is a trip to Anfield without suspended captain Bruno Fernandes and defenders Harry Maguire and Luke Shaw after they were injured against Bayern.
"I am trying not to think about that," former United goalkeeper Peter Schmeichel told CBS Sports.