Kagawa has impressed in both of United's opening two games, which is reward for the work the club have put in identifying Kagawa as a key man in United's bid to win the title back.
He said: "We did a lot of work on Kagawa. Last season there was more authority in his game and his goalscoring was good from that position.
"I went to see him in the Final against Bayern and he was absolutely magnificent - his movement, awareness of a pass, awareness of space in front of him, he did everything.
"He was the sort of player we were looking for and that's why we moved."