Roy Hodgson admits he had concerns about Luke Shaw's fitness long before Louis van Gaal publicly criticised the teenage star for being out of shape.
United signed Shaw in a blockbuster £28million deal this summer, but the left-back soon found himself out of favour with his new club manager after he turned up to pre-season way short of fitness.
Van Gaal made Shaw train on his own in the United States, claiming the player was "not very fit" and unable to "perform" to the standards required of him.
It was a controversial move designed to spur the 19-year-old on to get back to peak physical condition.
Hodgson agrees with what Van Gaal had to say and the England manager revealed there were serious doubts about the former Southampton defender's condition during the World Cup, where he made just one appearance for the Three Lions.
"I must say watching him play in the matches for Southampton, he didn't seem to have too many problems coping with the physical side of the game," Hodgson said.
"But that doesn't mean to say he can't be fitter and if Louis thinks that he can get him fitter then I'm sure he will certainly have our approval.
"I think when he (Van Gaal) talks to (former Saints boss Mauricio) Pochettino then Pochettino will say to him: 'what you were saying to Luke Shaw is what I was actually saying to him'.
"He (Shaw) might have had it mentioned to him a couple of times during the World Cup when we were together by people like myself and (England physio) Gary Lewin."
Shaw had no problem with Van Gaal's criticism and in fairness to the 19-year-old, he looked a lot sharper towards the end of the tour.
Unfortunately for him, he then sustained a hamstring injury that has prevented him from making his United debut and has also ruled him out of England's upcoming double-header against Norway and Switzerland.
Hodgson feels Shaw will have to work hard to get himself back up to the standards required of an England and Manchester United regular.
"I think a lot of Luke's situation is purely down to the fact that he is still young, his body is changing but I think he's aware that the work rate which is required does mean that he's got to work very, very hard on that aspect of his game," said Hodgson, who handed Shaw his first England cap in March before picking him for the World Cup ahead of Ashley Cole.
"I think he's been aware of it, Luke, and he will get fitter and stronger, not least because he's still a very young man and his body has not yet reached its proper proportions for the level he wants to play at."