The striker was brought to the club by Roberto Martinez in a £13m deal from Lokomotiv Moscow in January 2016.
However, Niasse was told he had no future on Merseyside after failing to impress Koeman upon his arrival at the club.
He was demoted the under-23's and stripped of his locker and squad number before being shipped out on loan to Hull, where his form picked up under the guidance of Marco Silva.
His Everton career seemed over but Koeman is now ready to give the forward a chance to shine, according to The Daily Mail.
Speaking at Finch Farm ahead of the Toffees' clash with Tottenham, Koeman said: "Sometimes in life you need to give opportunities. His behaviour has been perfect.
"He needs to fight like all the others."
“It’s not necessary to speak any more about what happened last season I found that now is the right time to bring him back to the first team."
Niasse was told again this summer he had no future at Everton but after a move to Crystal Palace broke down in the final hours of the transfer window, he is now needed to bolster Koeman's attacking options.
Everton signed Malaga's Sandro Ramirez in the summer but failed to bring in another forward after selling Romelu Lukaku to Manchester United.
