It was a grim watch. The reaction on social media was even more difficult to stomach.

Nobody deserves to be humiliated in front of 75,000 people. In no other walk of life would someone who is not good enough at their job be publicly shamed, like a scene from Game of Thrones, so why is it acceptable for it to happen to a footballer?

Diogo Dalot is not good enough to be Manchester United’s first-choice full-back. That has been ostensibly clear for much of the Portuguese defender’s eight years in England. But his persistent omnipresence in the starting XI is not on him.

For United supporters to jeer and boo him as he was substituted in the second half against Aston Villa – after a particularly poor display that saw him needlessly concede a penalty – is completely unwarranted. Michael Carrick keeps picking him, even deploying him out of position. Furore should be directed at the owners’ unfathomable neglect of a defence that has shipped more goals than any other team in Europe’s top-five leagues this season.

United fans have got previous and therefore should know better. When Joshua Zirkzee was substituted in the first half after a particularly below-par performance against Newcastle two years ago, supporters laughed and cheered at his withdrawal, sending the Dutchman straight down the tunnel, looking like a broken man.

Supporters felt so bad at their mistreatment of another human being that Zirkzee’s reappearance was greeted with rapturous applause at every opportunity in the months that followed, something the player himself was buoyed by.

Why do it again? Other players have been booed before. Paul Pogba and Marcus Rashford spring to mind as those who faced further unsavoury treatment from their own. While also completely unjustified, both players were targeted as a result of fans being unhappy with their application and effort, rather than their ability.

Dalot is a consummate professional. He faces the media more than most, willing to front up in times of perpetual crises, while other more household names have barely said a word.

Every week, he gives his all. He has been part of some of the worst United teams in their illustrious history, but he never wavers in his levels of intensity.

Social media is never a reliable source to act as a barometer of reason. Hiding behind their keyboards, particularly unscrupulous football fans can say what they really think, without thinking of the effect on the target. Forgetting footballers still have feelings is a tale as old as time. To some online supporters, football earn so much money that they should be able to take such a humiliation.

“We’ve got to be careful with that,” Carrick said of the incident. “I understand the frustration, I understand the disappointment of the supporters. We’re all frustrated, we’re all disappointed, and the players are as much as anyone, I guarantee you that.

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“Diogo, he gives absolutely everything. He’s played in different positions, he’s played left-back, he’s played really well at times. He gives a penalty away, he knows that. Maybe he can do a little bit better, all right, that’s part of it, he’s made a mistake, but he cares an awful lot and he’s giving everything.

“I like what he brings to the team, I like what he brings to the group and  I like what he brings to the whole environment and the culture that we’ve got.

Such an appraisal is perhaps why United are where they are: the acceptance of mediocrity. But senior figures at the club are to blame for that, not the players themselves.