Joe Gomez and Virgil van Dijk's long-term knee injuries have given Jurgen Klopp plenty to ponder in terms of his selections at centre back over the coming months, with the Liverpool manager having to may now turn to youth.
Gomez, 23, underwent successful surgery on Thursday after sustaining a serious knee injury during England training the previous day, with Liverpool hopeful he will be able to play some football again towards the end of this season.
However, with Van Dijk having also picked up a long-term injury knee against Everton in October, Liverpool can now call upon on just one experienced central defender in Joel Matip, who himself only returned from injury in Sunday's 1-1 draw at Man City.
Klopp had initially used holding midfielder Fabinho as a makeshift centre back following Van Dijk's injury, only for the Brazil international to then pick up a hamstring problem in the Champions League against Midtjylland.
And with Dejan Lovren having left Anfield in the summer, Klopp is now short on experienced alternatives to cover at the back
Here, we look at some of the standout young defenders in Liverpool's ranks...
Liverpool's upcoming games
- Nov 21: Leicester (h)
- Nov 25: Atalanta (h)
- Nov 28: Brighton (a)
- Dec 1: Ajax (h)
- Dec 5: Wolves (h)
- Dec 9: Midtjylland (a)
- Dec 12: Fulham (a)
If Liverpool are to look to their youth ranks for cover at centre back, it seems Rhys Williams is likely to be the first player Klopp would turn to. The 19-year-old made his Liverpool debut in September, starting alongside Van Dijk and then being partnered with Fabinho in the second half, as the Reds beat Lincoln 7-2 in the Carabao Cup, and played again in the defeat to Arsenal in the next round.
Meanwhile, the England U21 international has also featured in Liverpool's three Champions League group games so far this season, including starting their most recent clash in Atalanta, with the Reds having kept clean sheets in all three matches.
Part of Liverpool's 2019 FA Youth Cup-winning side, Williams signed a five-year contract earlier in 2020, underlining the club's belief in his potential.
- Joe Gomez out of England squad with knee injury
- Fabinho off as Liverpool suffer another injury blow
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Williams - who has confessed to studying Van Dijk's performances and post-match analysis of the Dutchman's displays - had a loan spell in non-League last season with Kidderminster Harriers and made his England U21 debut this month.
"He did really well," said Klopp after Williams came on as a sub against Midtjylland in October. "The only problem now is we have four days until the West Ham game, you will make a story of him every day and then he has to prove he can deal with that again. Everything was calm around him. We will try to do that as well.
"To be really clear and positive, Rhys was not in one situation tonight a problem for us, he played a really good game."
Sepp van den Berg
Netherlands youth international Sepp van den Berg could also be in contention. He made four first-team appearances for Liverpool last season in the FA Cup and Carabao Cup and travelled with the team to the Club World Cup.
However, the 18-year-old - who had also attracted interest from Bayern Munich when he signed for Liverpool in June 2019 - may now be behind Rhys Williams in the pecking order after missing out on a Carabao Cup runout this season.
Van den Berg already has some top-flight experience under his belt, having made 22 Eredivisie appearances with former side PEC Zwolle. "I am calm with the ball, I am quite quick and can run," he said on his arrival at Liverpool, who insisted at the time he was not an 'academy' signing but a player they were looking to develop for the first team.
Nat Phillips made his Premier League debut for Liverpool in their recent 2-1 home win over West Ham, even earning the man-of-the-match award from Sky Sports pundit Jamie Carragher after a solid display.
The defender had looked like he was on his way to the Championship before the transfer window closed in October, with Middlesbrough, Nottingham Forest and Swansea all weighing up a move for the 23-year-old, but ultimately he remained at Anfield to provide extra cover at centre back.
Phillips had two loan spells at Stuttgart last season, where he made 19 starts in Bundesliga II, and in between he was recalled by Klopp in December when Matip, Lovren and Fabinho were all out injured at the same time.
Klopp said he had been impressed by Phillips's performances in Germany and he went on to start the FA Cup win over Everton in January, before returning to Stuttgart for the remainder of the season.
He is not currently in Liverpool's Champions League squad, however.
At just 17 years old, Billy Koumetio is the youngest player listed here - but the Frenchman is highly rated at Liverpool.
He signed his first professional contract in August and went on to impress Klopp and his team-mates during preseason. However, a tough afternoon in a friendly at Blackpool may suggest it is too soon for him to step into the fold.
Koumetio was dispossessed for Blackpool's first goal and played an attacker onside in the buildup to them winning a penalty for their second, before he was replaced at half-time. Liverpool bounced back to win 7-2 and afterwards Klopp conceded the defender still had things to learn - but backed him to improve.
"I'm pretty sure he will make big steps," said Klopp this summer. "We just have to make sure that we really deal with his age group and physical demands well." But for an ill-timed injury he may well have figured in the Carabao Cup this season. For now though, he is still to make his competitive first-team debut.
An experienced alternative?
Alternatively, Klopp might be tempted to repurpose another of his midfielders as a centre back - as he did with Fabinho - thereby ensuring Liverpool maintain plenty of experience in their backline.
If he decides to go down this route, the most obvious candidate to drop back would be Jordan Henderson. The club captain plays an important role in Liverpool's midfield, but Klopp has more bodies in that area following the signing of Thiago Alcantara in the summer.
Plus, Henderson has some experience of playing at centre back having stepped into the role in the FIFA Club World Cup semi-final against Monterrey last year. Liverpool team-mate Adam Lallana described his performance as "magnificent" that day as he helped the Reds secure a 2-1 win and Klopp was similarly impressed.
"If the manager needed me to go there again," added Henderson, "I would do it."
Sky Sports pundit Jamie Redknapp told the Pitch to Post podcast:
"I'm choked for Joe Gomez if it is a bad injury. He's a young man who has already had knee injuries and come back brilliantly. I'm a big fan of his, he seems like a really good, down to earth player.
"I remember seeing him many years ago playing for Charlton in the FA Youth Cup and thinking 'this is a star of the future' and he's certainly proved that at Liverpool. I just hope it's not going to be anything too serious.
"From an England point of view, it's a disappointment for Gareth Southgate, but for Jurgen Klopp, if this is a long-term one and you've got no Virgil, no Joe Gomez, that puts an enormous amount of stress on this squad from a team that were red-hot favourites at the start of the year.
"It's certainly going to change things and for everybody else involved, that back two have been so impressive at times. It's not been easy with no Virgil at the moment, but no Virgil and no Gomez is going to make it even more difficult.
"I suffered with injuries playing for England and it's really hard to deal with because you're so proud that you're there but you also know it's costing you an enormous amount of time in your career.
"I broke my ankle twice playing for England, tore my hamstring playing for England, it cost me an enormous amount of time. Of course you wouldn't swap it for the world but there is something so frustrating because it should be the highlight to play for your country but when you come back injured, it's frustrating for everybody."