Newcastle collected around in £130M for the Sweden striker after he went on strike in an attempt to force a move to Anfield in the summer, funds which they put into the moves for Yoane Wissa and Nick Woltemade.
However, Isak has been weighed down with numerous injuries and has not been able to get to his best with the side who have relied on fellow striker Hugo Ekitike for goals.
Speaking ahead of the Newcastle clash, Slot confirmed that Isak will not only not face his former side but is also not on the pitch just yet.
“He's not even on the pitch yet.
“I think it's called a walker, he's just out of his walker, so that tells you that he's not on the pitch and not expecting him on the pitch today or tomorrow in terms of his recovery work,” Slot said.
“That's going to take a while before he's back, as we knew.”
Isak is currently recovering from a fractured fibula and ankle ligament damage left many fans wondering whether he will ever live up to his price tag.
The Reds still have not won a top-flight game in 2026 and will aim to pick up their first 3 points against the Magpies who come off the back of last weekend's 2-0 home defeat to Aston Villa.