Nevertheless, the Sweden international is now poised to make his comeback for the first time since he fractured a bone in his leg when being tackled by Micky van de Ven during his side's 2-1 win over Tottenham just before Christmas. Speaking on the eve of the fixture, Arne Slot confirmed that while Isak won't start in Paris, he could feature if needed.
He said: "He finished close to a week of team training sessions; he can play a part, otherwise I wouldn't take him.
"I didn't take him to the Etihad because we felt he wasn't able to get a performance yet. We think we can get a performance out of him now, but not to start."
Nevertheless, Liverpool will be without Alisson Becker, Conor Bradley, Wataru Endo, Stefan Bajcetic and Giovanni Leoni for the fixture. Alisson is expected to return before the end of the season, but Bradley, Endo, Bajcetic and Leoni are unlikely to make a comeback until next season.
Meanwhile, Bradley Barcola, Fabian Ruiz and Quentin Ndjantou are all expected to miss out for PSG.
Luis Enrique explained: "If he’s [Barcola] still unwell, he won’t play tomorrow. “He had a partial training session yesterday and a full session today. He’s coming back. We’re finding the best conditions. He’ll tell us when he’s ready. He’s lacking a little confidence.
"We're going to try to have the ball more than Liverpool, a very good team with quality players and a very good coach. It'll be difficult.
"In the quarter-finals, it's naturally a special game, because there are just eight teams. When you start to get used to being at this level, it's great as a team.
"It's, of course, positive to be able to show it against Liverpool. What we want is to qualify. We're aware of the difficulty, but we're motivated. We want to enjoy playing at the Parc."