Alexander Isak will return to Liverpool training on Friday ahead of this weekend's showdown against Manchester City but manager Arne Slot has pleaded for patience with the club's record signing.

Isak, who signed in September from Newcastle for a British-record fee of £125 million ($164 million), has not played since coming off at half-time of the Champions League win in Frankfurt last month.

"He will train for the first time today with the team again, after being three weeks out," Slot said at his pre-match press conference on Friday.

"I know that I said three weeks ago that his pre-season has ended so now it's time for us to see where he is.

"But I have to come back to those words, because if you are three weeks only with the rehab, that doesn't bring you back to the levels he was three weeks ago."

Swedish international Isak has played just eight games for his new club since arriving at Anfield on transfer deadline day, and is yet to score a Premier League goal.

Slot said the 26-year-old, who has been sidelined with a groin injury, would need time to get match fit.

"You cannot compare rehab with games of football or training sessions with the team," said the Dutchman.

"As much as we try to replicate it, that's simply not possible. So, again I have to say, give him some time."

Slot also said he expects goalkeeper Alisson Becker to be available again immediately after the international window that follows the City match.

City and Liverpool have dominated English football over the past decade but this year both clubs are playing catch-up with Arsenal, who are six points clear of Pep Guardiola's second-placed team.

Champions Liverpool are a further point behind after a win against Aston Villa last week ended a four-match losing run in the league.

They followed that up by beating Real Madrid impressively in the Champions League on Tuesday.

Slot was asked whether Sunday's game was a "must-win" for both teams given Arsenal's lead but he said his main focus was on achieving consistency.

Liverpool started the season with seven straight wins in all competitions before losing their way badly from late September.

"We've won two (against Villa and Real Madrid), so our focus is on getting consistent and improving, getting players fit, and then we will see where that will lead to," said the Liverpool boss.

Slot said he was looking forward to pitting his wits against Guardiola at the Etihad. He said many teams had changed their tactics against his side this season but City's style was predictable.

"What I like about Pep Guardiola's teams is that you get 10 out of 10 times what you were hoping for -- a great game of football with no time-wasting and all kinds of things that I start to dislike more and more about football," he added.

"But these are not the things you can see if you're watching a Man City game."