In the biggest moments of the season, you need your captain to stand up and be counted. Bruno Fernandes wilted at Anfield at the weekend and epitomised everything that was wrong with his side on the day.
A week after the biggest high of his United career, lifting a trophy at Wembley, he arguably reached his lowest, being the face of a thrashing for the ages.
Erik ten Hag refused to single out any of his players for public criticism after the match, but Fernandes was rightfully hung out to dry by pundits at full-time after wearing the armband during the aberration.
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"It was a shambles, epitomised by captain Bruno Fernandes, who has been embarrassing at times," legendary captain Roy Keane said afterwards.
"They've not understood the dangers of this fixture. The Manchester United players have been eaten alive out there."
If there is someone who knows what it takes to captain United it is Keane, and his damning assessment of Fernandes has to cast doubts over his long-term suitability for the captaincy.
Only a fortnight ago, this writer backed the 28-year-old to be made permanent captain at the end of the season, and while he has largely enjoyed a successful season, this certainly planted the seed of doubt.
The captain should set the standard for the rest of the team to follow and be the leader on the pitch. They should be the ones who lift heads when they are down and rally their teammates to fight to the very end—everything that Fernandes failed to do at Anfield.
Instead, the man with the armband performed like a petulant child, irate at everything going against his side and throwing his toys out of the pram as United were dismantled by their fiercest rivals.
He was theatrical in his complaints to his teammates and was constantly moaning at the referee, almost oblivious to the downfall of his side and failing to take responsibility for their embarrassing display.
"Fernandes' body language today was nothing short of disgraceful," Keane added.
"A really talented boy, he's your captain, but his body language, waving his arms, not running back... you wouldn't be happy with him in your dressing room."
There were moments when he, like many of his teammates, appeared to give up completely and didn't do the very basics expected of them.
When substitute Stefan Bajcetic darted past him in the second-half, the Portugal international stopped in his tracks and accepted defeat rather than make any attempt to try and win the ball back.
It was these moments that were just as shameful as the scoreline, as a United side was not only embarrassed, but allowed it to get worse by throwing in the towel.
"I have had enough of Fernandes throwing his arms around, whinging at everyone, holding his face when touched," Gary Neville barked at full-time.
"That wasn't a captain's performance from a Manchester United player, and I am sure Erik ten Hag will deal with that."
What happens next is going to be fascinating. Ten Hag has already insisted he sees the result as a one-off, while Jurgen Klopp also admitted that it was a 'freak' result.
The real test for United will be how they respond to prove that is the case, and they could yet win another two trophies in the form of the FA Cup and Europa League.
It means there are still another two opportunities for Fernandes to lift silverware as captain this season too, and he now has his own point to prove that he is the right man to lead his side going forward.
Perhaps the one crumb of comfort is that nobody else proved a worthy challenger to the armband at Anfield, and while it is harsh to single out one player for criticism, the captain can't hide away from it.
Fernandes should have been setting the standards, but instead he lowered them.
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