Isak joined Liverpool in a British-record £125m deal on deadline day, bringing an end to the saga of the summer that saw the Swede go on strike at Newcastle.
The striker has yet to feature for the Reds having not played club football since the end of last season and was not in the matchday squad that scraped victory over Burnley on the weekend.
Slot, however, has revealed that there is a strong chance that he will make his debut against Atletico on Wednesday.
"Definitely a chance because he's in the squad," he said at his press conference ahead of the Anfield clash. "The chance to play, I would usually say 99.9 per cent sure but I can say 100 per cent sure he will not play 90 minutes but he's part of the squad.
"It's already a Champions League game to look forward to but if people look forward to his playing time that could mean that could happen tomorrow as well."
On the potential of Isak starting the game, Slot added: "The only thing we're sure of is he will not play 90."