Isak, who scored just his second Premier League goal of the season on Saturday in 10 appearances, has struggled since arriving at Anfield.
Earlier this summer, he was left out of Newcastle’s squad for their pre-season tour of Asia with what the club described as a “minor thigh injury”, while it was understood he wanted to explore an exit.
Isak then trained alone at his former club, Real Sociedad, before joining Liverpool on deadline day.
Without a proper pre-season, he arrived without match fitness and has only started 10 times in all competitions.
Liverpool also does not have Mohamed Salah, who is with Egypt in the African Cup of Nations, nor the injured Cody Gakpo.
Fellow striker Hugo Ekitike, who arrived in the summer from Eintracht Frankfurt, was also successful at Spurs and was expected to continue leading the line for the Reds.
The 23-year-old Frenchman has scored 11 goals this season, five of which in the last three league games were a factor in Isak starting on the bench.
