Scottish international Fletcher is suffering with an Achilles injury and could be out for several weeks.
Speaking of Wickham's importance to his side, Di Canio is quoted as saying by the Shields Gazette: "He's part of the squad and he's done very well at Sheffield. That's why he's got so many options.
"But at the same time, he's our player. He's been on the bench for the last two games and he would have come on against Stoke if Phil Bardsley hadn't got injured, which changed my plans.
"The decision at the moment is that he's our player and we need him here."
Wickham, 20, moved to Sunderland from Ipswich Town for £8m back in 2011 but has struggled to embed himself in the first team.
He scored eight league goals in 11 starts for Wednesday earlier this season.