Robin van Persie
Van Gaal says Van Persie was not replacement because of injury. Getty Images

Manchester United manager Louis van Gaal has denied Robin van Persie was substituted against Cambridge United because of injury.

Van Persie was replaced by James Wilson after 66 minutes of the 3-0 win over the League Two side and though he showed no clear signings of having picked up a knock, he walked down the tunnel immediately after being taken off.

Angel di Maria was also replaced in the second half at Old Trafford but Van Gaal has calmed fears the pair were taken off due to further injuries in the United ranks.

The United boss said: "I said already [to Robin] at half-time, 'I shall change after 60-70 minutes because I want you to play against West Ham United.'

"It's always difficult to play three matches in a week. I have given rest to five players. I think that when we have won, after the match I can say it was a very good decision.

"I gave van Persie a rest during the match and also Di Maria, and I gave Ashley Young minutes to play because he is back again.

"In the second half, I think we played better," the manager added. "We created many more chances but we didn't score. Robin van Persie had four possibilities to score, but [on the whole] I am pleased."

United have suffered 59 separate injuries during a harrowing first season under Van Gaal, with Michael Carrick becoming the latest absentee after he was ruled out for four weeks with a muscle rupture.

Such has been United's fortune with injuries that every one of Van Gaal's substitutions are heavily scrutinised, with Van Persie and Di Maria the latest players to have their withdrawal questioned.

As United set up a FA Cup fifth round trip to Preston North End, the club welcomed back Ashley Young, who was a surprise inclusion on the bench ahead of schedule after a hamstring problem.