Tuesday night's shock 1-0 defeat at Kilmarnock left the Hoops 10 points behind their arch-rivals with just 15 matches to play.
Even if they were to win the last two Old Firm derbies of the season, they would still need Rangers to slip up badly to complete a sensational comeback in the title race.
Fortune said: "Now we have to win every game that is coming.
"It will be difficult but we can do it. Why not?
"We've shown that we are a big team, play very well and have a lot of chances.
"We have to complete that with goals and not conceding.
"We will do it, I'm confident about that."