IFAB Law 12 states that players must remain in the dressing room or a spectator area until a match is concluded. However, that is not denoted by the full-time whistle.

Instead, the officials must have formally left the field; otherwise, it constitutes an unauthorised pitch entry and misconduct. As a result, the match official could report Cunha for his return, which could result in further action, such as an extension of a ban or a fine, depending on the player's behaviour.

As Cunha celebrated with his teammates, United boss Michael Carrick encouraged him to depart the pitch. That provoked an angry response from the Brazilian, who had to be guided off the field.

Carrick's intervention might not prove enough, after Cunha was also spotted watching the final minutes of the match from an advertising board rather than relocating to the confines of the stadium. But the United boss will have been impressed with the former Wolves star's impact before that.

The red card will see Cunha miss United's next Champions League match against Sporting CP next month. It remains to be seen if further action is taken over his failure to leave the field.

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"It's a win for us as a football club. To see the supporters go home happy is what we live for, to give them performances and nights like this so they can get back again energised," he said at full time.

"As a team, we've shown a lot of character to weather what we've had to. You find out a lot about each other. The players will find out things about me, I certainly do about them and their character, what it means to them and what they're prepared to put in.

"Tonight was right at that moment. It depends what happens next, we've got to make the most of it, we've got to move forward but I'm feeling a lot better about things tonight."