The Dutch fullback struck on debut in victory over Wigan Athletic yesterday.
"Some of Büttner's play was good but I think he was a little bit rash at times," the manager admitted to MUTV. "He has a great engine and great enthusiasm for the game but he's raw with a lot of rough edges there.
"We think we can develop that and hopefully he can be a really good addition to the team. He scored a lot of goals in Holland and was determined enough to get that goal. It was a little bit lucky, I don't know if it got a deflection or not, but he showed his willingness to get in there and deserved it."