Muller explained in an interview with Bild that the Dutch specialist played a big role in the success of his career so far and that not many coaches would have put so much faith in youngsters at such a big club.
“I am very grateful to Van Gaal. The help I received under his leadership has brought me the results I see today,” said the 21-year-old.
“Not every coach would have expressed confidence in such a young player like me. Someday I will thank him personally for everything he has done for me."
Van Gaal was relieved of his post with the Bavarian club just over a week ago following a run of disappointing results in the Bundesliga, which saw the champions slip out of the title race and into a battle for Champions League qualification.