The Scotland international has been plagued by fitness issues for much of the campaign, scoring just three goals in 13 Premier League starts due to a string of injuries.
|3/1||Sunderland are 3/1 with Paddy Power to avoid relegation|
"I don't think Steven Fletcher's going to be available this season," the Uruguayan said. "We'd hoped he might be able to make the last few games but I'm changing my opinion on that now."
Sunderland approach Saturday's visit of Everton bottom of the Premier League, seven points adrift of safety with as many matches left to play, but Poyet, despite claiming his side needed a "miracle" after losing to Tottenham, insists he will not give up hope of survival.
"I am still here until the last minute believing it is going to be a possibility," he added.
"It is a big challenge, it is really, really difficult - people were saying even impossible - so we will see."