Manchester United boss Louis van Gaal played down Robin van Persie's reaction to his substitution during victory over FA Cup opponents Cambridge United.

Van Gaal was happy to see his team avoid the same fate as Chelsea and City, who were eliminated by Bradford and Middlesbrough respectively.

"I am very happy," Van Gaal said.

"If they had scored the first goal then it would be a very difficult game.

"But I am very pleased because it was 3-0 and we have a clean sheet and we are in the next round."

The only slight disappointment for Van Gaal was the performance of Van Persie, who came off in the 66th minute and went straight down the tunnel.

"Robin van Persie had four possibilities to score," Van Gaal added.

"But I am pleased because you have to beat your opponent and then you are in the next round.

"I took him off because I want him to play against West Ham (on Sunday)."