The recent acquisition from Vitesse Arnhem acquitted himself well during the 2-1 win over Tottenham Hotspur and is likely to provide cover and, ultimately, competition for Patrice Evra at left-back.
"He's been training all week with us and have been very impressive," revealed Evans to MUTV. "He looks comfortable on the ball and is good in the tackle.
"He probably didn't get as much of the ball as he would have liked but he defended really well which was important so I'm sure he can be happy with himself."
Under-21s coach Joyce feels Büttner will only improve with more game-time at United.
"It's a good start for the boy," Joyce stressed. "He's not had a lot of football games and his pre-season has been a bit mixed up really as he was a little unsettled. So it's good for him to get a game under his belt and he started well. He'll only improve with more games and more fitness."