Both forwards withdrew from international duty during the recent break and returned to Liverpool for further assessment after picking up injuries with Sweden and the Netherlands respectively.
Isak’s problem was described as minor after he left the Sweden squad with a thigh issue, while Gakpo suffered an ankle injury during the Netherlands’ victory over Serbia.
Liverpool could be without both players for their meeting with the Premier League leaders, leaving the club with limited options in attack.
Hugo Ekitike remains a long-term absentee with an Achilles injury, while Federico Chiesa has yet to feature this season after suffering an injury towards the end of pre-season.
Lewis Koumas could therefore be the only available natural senior striker if Isak and Gakpo are both ruled out.
Liverpool head coach Andoni Iraola confirmed that neither player had yet been cleared to return, although he stopped short of giving a definitive timeframe for either recovery.
“I think Alex Isak and Cody Gakpo both have had to leave the national teams with injuries,” Iraola said. “Now it's a matter of if they are going to recover in time to help us in the next game or not. But right now they are both injured.”
Liverpool return to action against a Manchester City side that have made a perfect start to their Premier League campaign.
Iraola knows his team will need to produce their best performance if they are to become the first side to take points from City this season.
“I think we need to be very, very good if we want to beat City because they've been especially offensively scoring a lot of goals lately,” he said.
The Liverpool boss also believes his players can compete for major honours in the future, provided they continue to develop under his management.
“I don't know where this will put us but I'm sure that if we can give these players a good platform, a good structure, we will be there fighting for the titles,” Iraola said.
Liverpool have made an unbeaten start under Iraola, but the fitness of Isak and Gakpo could now become one of the biggest selection issues before Sunday’s meeting with the leaders.