The Reds star will almost certainly miss Sunday's blockbuster clash at Anfield through injury, leaving uncertainty over who will step in at right-back.

That’s the dilemma facing Jurgen Klopp this weekend, following the news that Trent Alexander-Arnold is almost certainly out of Liverpool’s Premier League showdown with Manchester City through injury. 

Alexander-Arnold suffered an adductor problem in training on Monday, ahead of the Reds’ Champions League game with Porto, and is set to miss Sunday’s game, as well as the forthcoming internationals with England. 

Bad news indeed, for the league leaders. The 22-year-old is one of Liverpool’s key players, his delivery from right-back one of the game’s deadliest weapons. His absence will be keenly felt against Pep Guardiola’s side.

What will Klopp do without his creative hub, then?

James Milner

The most obvious solution will be to ask James Milner, Liverpool’s Mr Reliable, to step in at right-back.

The 35-year-old did so against Porto, having impressed up against Crystal Palace and Wilfried Zaha earlier in the month, when Alexander-Arnold was ruled out through illness.

Milner, as he tends to, delivered in Portugal, providing an assist for Sadio Mane and keeping the lively Luis Diaz in check. 

His experience, tenacity and nous make him a key figure at Anfield, despite his advancing years. And the fact that Klopp chose to take him off 24 minutes from the end against Porto suggests he will be asked to go again on Sunday.

He is not a natural full-back, by any means, and there is still a fear that genuine pace could expose him, but rarely does he let his side down when asked to fill in there. 

Against his former club, he looks the standout option.

Joe Gomez

Another option available to Klopp would be to ask Joe Gomez to move across to right-back. 

The England international has played there plenty of times in the past, and replaced Milner against Porto, though it was always expected that he would eventually settle as a centre-back, which he has. 

Gomez certainly has the pace and the size to be a solid option if needed, though replicating Alexander-Arnold’s passing range and attacking output would be a huge ask for the 24-year-old, who has only started two games since returning from a serious knee injury himself.

Mind you, we’d love to see him up against Raheem Sterling, wouldn’t we?

Neco Williams

Could Klopp turn to youth instead? Liverpool have been boosted this week by the return of Neco Williams, the Wales international having recovered from his own muscle problem.

The 20-year-old made 14 appearances last season, but has not started a game since the defeat to Fulham at Anfield in March. In fact, his only competitive outing since then was as a stoppage-time substitute at Old Trafford in May.

Unlikely, then, that Klopp would throw him straight into the biggest game of his career, where he would be up against the likes of Sterling, Phil Foden and Jack Grealish.

 Williams, instead, will be looking at the Carabao Cup fourth-round tie at Preston later in the month, though the emergence of young Northern Irishman Conor Bradley, who started the third round win at Norwich, presents a fresh challenge in that regard.

What about a curveball? We often talk about right-backs playing on the left, but rarely is a natural left-back asked to move across to the opposite flank.

Liverpool have two stellar left-backs, with Kostas Tsimikas impressing in the early weeks of the season as deputy to the brilliant Andy Robertson.

Could one of those two switch sides? Robertson started at right-back for Scotland recently, although the experiment was short-lived. 

Both he and Tsimikas are exclusively left-footed, which would present a big problem in terms of balance, though their pace, energy and knowledge of the positioning needed to play full-back would be more than useful, especially considering City are likely to play the right-footed Grealish on the left.  

It would be a surprise, to say the least, if Milner is not the man tasked with filling Alexander-Arnold's shoes on Sunday.

The veteran has so often been asked to showcase his versatility, and the fact that he was withdrawn early against Porto shows Klopp's thinking. Gomez is an in-game option, and may have his eye on a starting place at centre-back in any case, but it would be a huge risk to ask either Williams or Tsimikas to step in for a game of such magnitude

In midfield, Curtis Jones will surely have done enough to keep his place after a brilliant display in Portugal, while Roberto Firmino will be eyeing a recall after his two goals off the bench.