The 20-year-old is currently on a season-long loan at Sunderland and has scored four goals in his last three games for the Black Cats.
Sunderland boss Steve Bruce has admitted that he would like to make the youngster striker’s switch permanent.
Ferguson told The People: “He’s doing brilliantly and he comes back to us at the end of his loan.
“The boy is a fantastic talent but the problem for Danny was that he wasn’t getting enough football.
“You had to go back to our youth games, two-and-a-half years ago, for the last time he played more than four games in a row. He also had problems in growing, in terms of his strength.
“He missed a lot of football because of that. I said that to him last season when I sent him to Preston on loan.
“Then he got injured and had to have a knee operation. That could have been down to a lack of strength in his thigh and knee area.
“But the strength is starting to come now. His physique is settled now and he’s starting to put on muscle.
“He’s a big, big lad – 6ft 2ins or 6ft 3ins. He played well against Chelsea and Everton.”
