The Premier League refereeing body has admitted an "error of judgement" in awarding Erling Haaland's winner in Sunday's Manchester derby.
Manchester City ran out 1-0 winners at Old Trafford despite having Phil Foden sent off in the first half.
The win maintained City's perfect start to the season, leaving them second in the Premier League table on 12 points.
For United, it was a second defeat in four league games. But they were left fuming that Haaland's goal was allowed to stand.
The City striker prodded home Josko Gvardiol's cross in the 60th minute. The goal was initially ruled out for offside; however, after a VAR review, the decision was overturned.
Why are United angry?
Although Haaland was onside, thanks to the boot of United defender Patrick Dorgu, United were incensed at the decision to award the goal.
United argue that another City player, Enzo Fernandez, was interfering with play immediately before Haaland scored. The City midfielder had attempted to head the ball before Haaland's decisive touch.
Fernandez was in a more central position and was clearly trying to connect with Gvardiol's cross. The Argentina international was standing in an offside position in the build-up and also appeared to be offside when he attempted to score.
A statement published on the Premier League Match Centre's X account during the game read: "VAR checked the referee's call of no goal for offside and determined that Haaland was in an onside position and recommended that the goal was awarded. The VAR also deemed that while in an offside position, Fernandez didn't play the ball."
United defender Lisandro Martinez, who was the closest defender to Fernandez during the incident, said the fact that the goal was allowed to stand was an "injustice".
"I think it was offside," United defender Lisandro Martinez told Sky Sports.
"And what I can't understand is the rules. He [Fernandez] was there; I went to him. He was there, in front of me. So that's why [Erling] Haaland was free at the back.
"Every season [the referees] are coming to our club; they explain for one hour, one hour and a half, the rules, and they look so confident with that, and then after five, six people make these kinds of mistakes in the Premier League. It's unacceptable.
"Because it's the best league in the world, you have the best teams in the world, the best players in the world, and now we have to go home with this injustice."
Pro Ref response
In a statement, Pro Ref said: "It was established that Enzo Fernandez did not play the ball and therefore that makes any offside offence subjective.
"However, on this occasion, the VAR did not recognise the likely impact of his position and should have recommended an on-field review."
"Contact has been made with Manchester United this evening to acknowledge what we deem is an error of judgement. A review of the incident will take place."
The National's sports editor's verdict
The fact that Pro Ref has acknowledged the error is a positive step, but will do little to appease Manchester United.
The goal was initially disallowed for the wrong call: Haaland was judged to be offside when he wasn't.
So why wasn't the goal disallowed for the right one?
There is an adage in football that if a player isn't interfering with play, then why is he even on the pitch? In this instance, it seems to ring true.
The offside law deems a player is offside if they are "clearly attempting to play a ball which is close when this action impacts on an opponent."
Fernandez is in the centre of the goal, in United's six-yard box, flinging his body forward "clearly attempting to play a ball". If he had connected and scored, the goal would almost certainly have been disallowed for offside.
He is occupying a space where a United defender – Martinez – must track his run, and United goalkeeper Senne Lammens must anticipate his connecting with the ball.
United boss Michael Carrick said: "If that's the interpretation of not interfering in the game now, that's really worrying for me. It's a staggering explanation."
The VAR should have sent referee Michael Oliver to the monitor for the subjective offence by Fernandez.
Admittedly, it would have created a bizarre situation in which a disallowed goal was being reviewed to remain disallowed, but these are the anomalies that technology was introduced to address.
City may argue that Foden's earlier red card was harsh, and that Bruno Fernandes needs to have a serious look at himself for his reaction, but it's harder to argue that United don't have a case for Haaland's goal being chalked off.
