Brighton enjoyed a number of chances and spells of possession in a first half they controlled at Old Trafford, only for Cristiano Ronaldo to fire the hosts ahead six minutes into the second half, with their hopes of a comeback dashed as Dunk was shown a red card shortly after.

On-field referee Peter Bankes initially showed a caution to the Brighton defender, whose heavy touch saw him catch Anthony Elanga on the edge of his own box, with Adam Webster's proximity seemingly saving him from having denied a clear goalscoring opportunity.

However, after consultation with VAR official Jarred Gillett, Bankes was sent to the pitchside review monitor at which point he upgraded Dunk's punishment to a red card.

Speaking in a one-off Ref Watch, former Premier League referee Dermot Gallagher told Sky Sports News: "I think it's a real good case of VAR working. On-field, without doubt, you'd give a yellow card, because by the time Elanga hits the deck, Webster is across. I can understand Peter Bankes' decision.

"You see Elanga picks Dunk's pocket, he's in possession, the criteria is is he in possession of the ball? Yes. Is he bearing down on goal directly? Yes, it's very close to the edge of the D.

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"Has an obvious goalscoring opportunity been denied? That depends on whether you consider Webster is coming across.

"What you'd say is, if Elanga takes one more step, he has a clear shot on goal. So I think Webster won't catch him there. He may if he decides to dribble on, but he doesn't have to - he can shoot at goal, and once he gets that shot it's a clear goalscoring opportunity."

Man Utd charged after players surround referee

Manchester United have been charged by the Football Association with failing to control their players after Dunk's challenge on Elanga.

United's players surrounded the referee after the incident in the 53rd-minute of Tuesday's win at Old Trafford, pleading for the defender to be sent off.

The Brighton captain was shown a yellow card, but it was changed to a red following intervention by VAR.

Potter: I don't understand why VAR got involved

Potter felt his side deserved more at Old Trafford but lay some of the blame for their defeat at the decision to dismiss Dunk as one of two refereeing incidents he took aim at in his post-match press conference.

With Brighton pushing for an equaliser in injury time, United added a second thanks in part to a quick free-kick on the break after Alexis Mac Allister was penalised for a foul on Bruno Fernandes, a decision which the head coach felt would've only been given to the home side.

He said: "The red card was a yellow card live, Adam Webster was round on the cover, it was not clear and obvious that he could not get there. If the referee gave a red card live, I could've accepted it more, but I don't understand why the VAR's getting involved in a clear and obvious error when it doesn't look clear and obvious.

"I thought we were the better team in the first half. It is disappointing how the second half turned out. There is lots to be positive about and I am proud of the players. There is just a little bit of frustration there because it feels like a missed opportunity.

"The second goal is a foul on Alexis but it is what it is, you don't get those here. It looked like a push but we have to accept it."

Even with their man disadvantage, Jakub Moder hit the crossbar for Brighton at 1-0 down and Danny Welbeck wasted a headed effort as Brighton's performance threatened more than it provided for the visitors, who fell to a first league defeat since December 15 at Old Trafford.

Potter added: "We're frustrated. We had large periods of the game, but we didn't start the second half well, we gave the ball away and they punished us. Up until then, I thought we were probably the better team, first half especially.

"We're frustrated with the sending off, but we have to survive, you've got 10 men at Old Trafford. We dug in incredibly well, hit the bar, Danny [Welbeck] had a header, so I'm really proud of the players for what they gave, and a little bit frustrated because I thought we could've got something tonight."

Rangnick: Ronaldo's best performance in weeks

Ronaldo ended his worst barren run of scoring for more than a decade with the opener against Brighton, leading interim manager Ralf Rangnick to praise his performance as the best he had provided in some time.

The temporary United boss also explained what tweaks he made at the interval to help his side fire to glory, and secure a first league win in three games.

He said: "It was a good performance by Ronaldo. In the last few weeks, it was certainly the best performance by him and a very, very important goal.

"Everyone could see after the first half, it was not an easy game. They are very possession-based. It was difficult for us to get hold of the ball. We made a change and it paid off. In the second half, we were more aggressive and tried to intercept the ball.

"The question at half-time was do we change formation or how we attack? We decided to stick to 4-2-3-1 and told our wingers to attack their centre-backs. That meant our full-backs had to jump to their full-backs and that paid off. From then on, it was a different game."