Rene Meulensteen has praised the Dutch defender following his arrival from Vitesse but has backed Patrice Evra to put up a fight in order to keep his spot at left back
"We see him as an aggressive player who knows himself. He looks always at the future," he told Voetbal International.
The 23-year-old full-back signed a five-year deal with the Old Trafford club on Tuesday, after completing his move from Eredivisie side Vitesse.
And Meulensteen believes the Dutchman's potential will see him prove to be a shrewd buy for the Red Devils.
"We brought him in because of his potential. It's not without reason that he is on the brink of playing in the Dutch squad," Meulensteen said.
He added, "That's why I said: Buttner, that's not a bad player, when Ferguson asked me about him. United is three, four or five steps higher then Vitesse. On the training ground we will see quickly if he can cope with a higher level."
Despite waxing lyrical about the former Netherlands Under-21 international, the Dutch coach admitted that Patrice Evra will prove tough to budge from the first team.
"Patrice Evra is a very experienced left back. [Evra] will not let him play in the first team very soon," he insisted.
United is still without defenders Rio Ferdinand, Phil Jones, Chris Smalling and Johnny Evans for their game against Fulham on August 25.