The treatment room was even busier before the international break, when Luke Shaw and Rafael were also out.

Van Gaal’s predecessor David Moyes had to do without key players at times last year and the Dutchman is worried about the trend.

“This is a big concern, you are right, I think,” the United manager said when it was put to him that United had suffered a lot of injuries in recent years.

Ashley Young was the latest first-team player to join the injury list this week when he suffered a groin problem. Van Gaal demands a high level of intensity from his players in training, but the former Bayern Munich manager appears unwilling to reduce the workload on his squad.

“We have to evaluate how we train, but for the level I demand as a coach we need to train like that,” said Van Gaal, who often puts his players through double sessions.

“But the players have to adapt to that level and that’s the crucial thing. Because we have to grow and develop ourselves to the top of this sport, the Premier League.

“But I am always evaluating myself. That philosophy has brought a lot of titles, I’m sorry to say that.”

Chris Smalling, James Wilson, Sam Johnstone, Reece James, Jesse Lingard, Michael Carrick, Young and Marouane Fellaini are unavailable for the visit of QPR. Phil Jones is also set for a month-long layoff due to a hamstring injury he suffered during England’s 2-0 win over Switzerland on Monday.

After taking his summer spending past the £150m mark last week, Van Gaal still has plenty of options available though. Marcos Rojo, Daley Blind and Shaw could all make their first appearances for the club.

The United boss was giving little away regarding whether star striker Radamel Falcao would make his debut following his loan move from Monaco.

“I cannot tell if you he plays or not, because that’s our surprise,” Van Gaal said.

Falcao has only played 217 minutes for club and country since he suffered a serious knee injury in January. Van Gaal has no idea how long it will take for the Colombian to get back to his best.

“That’s a question we cannot answer,” Van Gaal added.

“That’s also dependant on form, shape and we cannot predict that.”