The Dutchman has made frequent appearances for the Red Devils since scoring on his debut against Wigan in September.
The 23-year-old told Sky Sports News: "I have played more than I had expected. New players tend to be gradually brought into the team at United.
"It is great to be on the training ground with such fantastic players everyday. It really improves you as a player."
United paid £3.9m for Buttner from Vitesse Arnhem.