Ferguson, who was speaking to an audience at the Citizens Theatre in Glasgow, said: "He was never a problem until he got married. He used to go into work with the academy coaches at night time, he was a fantastic young lad.
"Getting married into that entertainment scene was a difficult thing - from that moment his life was never going to be the same.
"He is such a big celebrity, football is only a small part. The big part is his persona."