The Italian claimed that former director of football at the Black Cats and chief scout Valentino Angeloni didn't sign the players that he wanted, which he believes was a major reason for their struggles at the start of last season.
However, De Fanti has revealed that Di Canio did have the final say on which players joined the club, and that he advised that he should have been removed from his role after Sunderland avoided relegation in the 2012-13 season.
He told BBC Sport: "Paolo had the final decision on every player. He always blames everybody else but himself.
"The biggest mistake of the club's board was not to listen to me and Valentino's suggestion not to confirm Paolo at the beginning of last season.
"Paolo was fundamental in saving the team from relegation, but not the right manager to lead what would have been a new group. Cracks inside the locker room were evident already then."
Di Canio has been out of management since his sacking by the Black Cats in September 2013.