In 2002, the United manager tried to sign the tempestuous Italian from West Ham but failed to land.
Speaking to magazine GQ in 2008, Ferguson revealed that it was one of his few regrets in more than 20 years at the club.
Ferguson said: "Di Canio would have been capable of becoming a truly great player at Manchester United.
"I mean, he was a great player. But when you have a player like Di Canio, who expresses himself as an individual, like (George) Best and Cantona did, and (Ryan) Giggs, (Wayne) Rooney, Ronaldo and (Dimitar) Berbatov do... we make heroes quickly here. Di Canio could have been in that category."