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
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 see him as an agressive player who knows himself. He looks always at the future," he told Voetbal International.
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"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 added.
United are still without defenders Rio Ferdinand, Phil Jones, Chris Smalling and Johnny Evans for their game against Fulham on August 25.