Fletcher has since undergone surgery and is now fighting to be fit for the start of the new season, but the absence of a man who had scored 11 goals before misfortune struck has proved costly with January arrival Danny Graham yet to get off the mark.
However, having secured the club's Barclays Premier League status ahead of Sunday's final day trip to Tottenham, former Swindon manager Di Canio is already planning for the new campaign and relishing the chance to work with last summer's £12million signing.
He said: "First of all, let him recover because he has had this surgery. Then I hope he is going to enjoy working with me.
"I am happy to work with him, but I hope he will be happy to work with me because he can improve a lot.
"If you understand that, until today, he has played only not to be relegated. He has to become a footballer for a team that wants to finish and establish the club in the top 10 every time.
"I hope he is going to keep on scoring like he has because he scored 11 goals and he is the top scorer.
"Sometimes I tell my strikers, 'under me, you're going to score more goals, probably, but maybe less sometimes. I don't care if you work hard'.
"In League Two, I had a striker score 11 goals, but we finished top. I had four players with 11 goals.
"There were other strikers in League Two with 28, 29 goals, relegated to the Conference.
"We have to work together and work so hard for the team's cause, for the club's cause."
Goals have been a problem for Sunderland all season - indeed, for several seasons, with Steve Bruce and Martin O'Neil having admitted their concerns over having to rely upon Darren Bent and 26-year-old Fletcher respectively.
It is a failing Di Canio acknowledges and while he will hope to improve that particular situation, he admits he will ask Fletcher to broaden the range of what he offers to the team.
He said: "I know him, I have seen him play many times. He scores goals, which is the priority.
"But in some games, if we don't score a lot of goals, we have to work hard to get point or a victory to give us the chance to push forward and stay higher in the table.
"For this, under me he can improve his football a lot. He will probably understand more, in my opinion, what it means to play with the team off and on the ball.
"For this, he has too feel excited to play under me, like I am very happy to have him in the squad."
Fletcher is one of few Sunderland players to have emerged from the current season with his reputation enhanced, with keeper Simon Mignolet also among a small band.
But for the Belgium international, the Black Cats could have been in even deeper trouble, and the 25-year-old has inevitably been linked with a big money move away from Wearside.
Di Canio said: "He is one of the best. It's clear, he's an international player.
"It's easy to understand the interest from clubs, but obviously we don't want to speak now about what can happen in the future because I want to be totally focused for the next game, which is very important."