Wickham, who scored eight goals in 11 Championship appearances for the Owls, has sat on the bench for the Black Cats in the past two Premier League fixtures and is now likely to get an opportunity under Poyet as Fletcher could go for surgery.
"It's affecting him more than I thought. I'm a bit worried about it," Poyet said of the Fletcher problem.
"We're analysing it with the medical staff. But we're going to have to make a decision one way or the other.
"We'll have to look at the games ahead and the chance of rest in between, but we'll need to make a strong decision.
"It probably makes it more likely that Connor will stay for longer.
"Connor has got plenty of admirers, you can't imagine how many. But he wasn't going anywhere on loan before the transfer deadline.
"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."
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