The Oranje boss has stressed that his side have no place for footballers who are not at the peak of their fitness ahead of the fixture with the Nationalelf next week
The Benelux nation selected a party of 23 men for next week's friendly but, according to the Oranje coach, four of them are yet to be given the green light to participate against Joachim Low's men.
"My team is based on the form and shape of the players, but there are also those that are unfit or already injured," the 61-year-old told reporters.
"Those places are still open [Jeremain Lens, Luciano Narsingh, Kevin Strootman and Marteen Stekelenburg]. I think a selection must be earned."
Van Gaal then went onto comment on the current situation of Inter midfielder Wesley Sneijder, who has been struggling with injury this season, and appeared to rule him out of contention until he regains his shape.
"Sneijder is not in that group of four because he has not played for six weeks," the former Bayern Munich and Barcelona boss added.
"He's fit enough to train, but not to play matches. Everybody has to be fit, we're not a rehabilitation centre."
The trainer's first match in charge of Netherlands ended in a 4-2 defeat to Belgium, but he insists a repeat performance will not be given against Germany as he believes he has found the nucleus of his squad.
"Back then, I had to get to know the players a little bit. Now that I know them, I don't intend to make a lot of changes to the team," Van Gaal concluded.