Manchester United manager Jose Mourinho has claimed that the officials "went against protocol" by disallowing a goal for his side during their 2-0 FA Cup win over Huddersfield Town this evening.

Juan Mata's strike right on the stroke of half time was initially given by referee Kevin Friend and his official, only for VAR to cancel it out due to offside against the Spaniard.

The decision was a controversial one with numerous replays showing that the offside was marginal at worst, and Mourinho believes that it went against the VAR guidelines which determine that technology can only be used for "clear and obvious errors".

"It is amazing when the truth comes. But also [there are] problems and one of the problems is exactly what happened today, which goes a little bit against the words of the protocol. The words of the protocol are something like a clear and obvious situation and for sure it was not a clear and obvious situation. But we know that it is experimental, and we have to accept. But I am speaking after a 2-0 victory," Mourinho told reporters at his post-match press conference.

"I am close to winning the best-behaved manager in the Premier League, so nothing that can make me lose that trophy this season. The feeling is a bit strange and I was sharing it with David [Wagner] on the touchline and [fourth official] Anthony Taylor, which is the moment of the doubt. We score a goal, I cannot be happy.

"David concedes a goal but he doesn't know if he goes to half time with 2-0 or 1-0, and it takes time and then the decision comes. So, we have to adapt to that waiting time and cope with the frustration when that decision goes against you.

"At half time I had to say 20 times to my analysts and assistants to shut up because I don't want the players to know what happened. I want the players to feel, 'Yes, it is offside and to move on', without being sad or unhappy. 'Shut up, we have to move on', but one day it will go in our favour."

United's eventual victory set up a quarter-final showdown against another Premier League side in Brighton & Hove Albion.