Japan boss Alberto Zaccheroni believes Kagawa has all the attributes to be a success at United.
He said: "I haven't offered him my congratulations yet. I've only said to him 'good luck' because this is just the start for him. I know he'll need results to be deemed a success at Manchester United.
"But I fully expect to congratulate him three years from now because he clearly has the mental strength and the technical ability to make it there."