Louis van Gaal 'angry' after United's draw with Cambridge United

“Of course it is frustrating. We made the same error as against Yeovil Town and against QPR, we did the same playing style more or less in the first half.

“Then I had to be angry again. In the second half we did much better and we are not out of the Cup. That is the most important thing.

“But the atmosphere here, the crowd, was fantastic. You know always in advance that all aspects in a game like this is against you.

“I was angry again but it is part of my job. I want to be very happy at half-time. But it was not always the same.

“We have to come here, the pitch is not so good, but that can influence also that you play in another playing style. The opponents are always giving a lot more than normal. And defending is always easier than attacking.

“Then you have seen the referee. It’s always the same. Everywhere I have coached these games and I have coached these games with other clubs. You can give your own opinion on the referee. I cannot give you mine.

“We know everything is against us. But to win you have to survive and I know also what I’ve already said that attacking is much more difficult than defending.”

Van Gaal did praise plucky Cambridge as he revealed he rested Wayne Rooney and Juan Mata. Rooney had tweeted on Thursday that it was a “dream” to win the FA Cup and wanted to play.

Van Gaal added: “I can only give the credit to the Cambridge coach, to the staff they did marvellous.

“The FA Cup is very important - it is the most important title for us. To win the Premier League is much more difficult now, so the FA Cup is our objective also.

“I gave Rooney a rest. He’s fit. And Mata is also fit, I give him rest.

Like I did with Carrick and van Persie in the match with Yeovil.”

Meanwhile, Cambridge boss Richard Money toasted his FA Cup heroes after claiming it was a “mind blowing” achievement to earn a replay.

“It’s going to be worth an incredible amount, it’s mind-blowing to be honest. I don’t know what it’s going to be worth. I think the chairman was probably hoping we didn’t score a winner!"

He added: “We made a real big thing about the names, and the shirt. We hadn’t experienced standing in the tunnel next to Falcao and Di Maria.

“They didn’t swap shirts I don’t think. We might buy them one now though! Not one of our players asked for an extra shirt. Not one.

“I’ve asked to get a couple of programmes signed for my grandson as everyone likes a souvenir at some point.”