Kagawa joined the Red Devils in a £12m deal from Borussia Dortmund and has enjoyed an excellent debut campaign in the Premier League, despite suffering a knee injury which kept him out of action for two months.
Ferguson told Sky Sports News: "He's doing very well for us now. He has fantastic composure on the ball and his decision-making is good.
"He seems to always pick the more sensible pass and for the first goal at West Ham he had the composure to take the player on in a tight area and roll the ball to Antonio Valencia for a tap-in."
Kagawa has made 23 appearances this season in all competitions for United, scoring five goals.