Owen is fit to face his old club for Stoke City today.
Ferguson said: "There was the case when I left Berbatov out of the European final. I looked at my subs and thought if I was a goal down with a minute to go who would I depend on? Berba or Michael? Michael won hands down, no doubt about that.
"He never missed a training session. Every morning he was always there. He showed a great desire to be part of the scene here.
"And he improved as a footballer, really. Technically he got better, even though he was in his thirties."