The Dutchman, who took over at Old Trafford after the World Cup, has won titles with the likes of Bayern Munich, Barcelona and AZ, and also led Ajax to the Champions League in 1995.
Rafael told Perform that the former Barca boss is a "strong coach" who has specific ways of working, but said that his glittering CV speaks for itself.
The Brazilian said: "Van Gaal is a strong coach. He admires the right things, he asks everybody to be on time for the activities, we can't be late, he likes to see us training hard.
"So, he has some differences [to former boss David Moyes], especially the philosophy and we need to be adapted to this, however it's something right and the proof is the titles that he won."
United travel to West Bromwich Albion on Monday.