The 26-year-old Scotland international was unused substitute for Tuesday night's 4-2 Capital One Cup victory over MK Dons after earning a surprise recall to the bench following five months out after ankle surgery.
Fletcher, a B£12million signing from Wolves last summer, went a good deal of the way towards paying off his fee with 11 goals before his first campaign on Wearside was cut short by injury in March.
For much of that time, Martin O'Neill played him as a frontman and while that paid dividends, successor Di Canio has revealed he will not be used in the same way this time around.
The 45-year-old Italian said: "I'm happy. I have always said I am happy, but I have to be really happy because he can join the team that can help him to be crucial, like he was.
"Last year, his goals were very important, but he can be even more crucial and play in some way for his team-mates because he has got talent, he has got quality.
"In the way we want to play, even if we are only at the start of our season and the beginning of our project, we are going to play not with him alone up front and hope that he can do something.
"Our system, our mechanism, attacking football, especially at home many times, we are going to put the ball into the box.
"Even in a game that wasn't very good or perfect at Southampton, we arrived there, but two or three times the ball was there in the first half and we didn't have a killer instinct, something that he has got."
Fletcher will be among the squad which travels to Crystal Palace for Saturday's Barclays Premier League fixture between the two clubs and while he has had no competitive football since his injury, Di Canio has not ruled out an appearance at Selhurst Park.
Asked how close he is to getting on to the pitch, the Black Cats boss said: "If he is on the bench, he can be involved straight away because he is ready.
"He is a crucial player because he is another important option, he is a very important player, but I will decide when I have the feeling that he can give the maximum to the squad, to the cause, to involve him.
"For me, the fact that he will travel with us tomorrow again and join the team, he is already involved. I have only to decide when to select him with the other 10 for the starting XI.
"But it doesn't mean he can't start on Saturday straight away. We will see, but anyway he will travel with us tomorrow because now he is part of the squad and we are happy to have him back."
Summer signing Jozy Altidore has been the focal point of the Sunderland attack so far this season with Stephane Sessegnon providing the support.
However, the constant speculation surrounding Benin international Sessegnon's future, coupled with his lack of form, has proved frustrating and his cause will not have been helped by the fact he has been charged with drink driving after being arrested in Newcastle during the MK Dons game, in which he was not involved.
Di Canio declined to confirm whether or not Sessegnon will be involved at Palace as a result of the allegation against him, but given his firm stance on discipline, his participation seems unlikely while the matter is ongoing.