Back in the early days of Jurgen Klopp's reign, the German was constantly juggling different centre-back partnerships.

That was often through choice, rather than necessity, as he struggled with a defence consisting of Dejan Lovren, Steven Caulker, Ragnar Klavan and an ageing Kolo Toure.

Fast forward, though, and the story of Liverpool's 2020/21 season can't be written without dwelling upon their injury crisis at the back.

Fate seems to have conspired against the champions' hopes of retaining their title, with Everton inflicting two hammerblows on their rivals' ambitions.

The Toffees' 2-0 victory at Anfield - their first away Merseyside derby win of the 21st century - will obviously have serious ramifications, not least because it was Liverpool's fourth consecutive home defeat in the Premier League.

Yet Jurgen Klopp might feel their earlier meeting of the season, which came in October, was even more destructive due to the season-ending injury suffered by Virgil van Dijk in a collision with Jordan Pickford.

Joe Gomez and Joel Matip have since joined him in the physio's office and a host of other setbacks have seriously hindered the defence's ability to gel.

Two Deadline Day signings haven't really helped. We're yet to see Ben Davies in action because... guess what, he's injured. And Ozan Kabak has really struggled in defeats to Leicester and Everton.

Just as it seemed things couldn't get any worse, Jordan Henderson was forced off in Saturday's derby, meaning Klopp was forced to use yet another new pairing in Kabak and Nat Phillips.

Over the course of the season, Liverpool have now fielded no fewer than 18 different partnerships at centre-back. Let's take a look at how they got on - we've ranked them by goals conceded per game.

18. Joe Gomez and Virgil van Dijk
Goals conceded: 9
Games together: 3
Defeats: 1
Wins: 2
Draws: 0
Goals conceded per game: 3
Win percentage: 66.66%

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17. Joel Matip and Rhys Williams 
Goals conceded: 2
Games together: 1
Defeats: 1
Wins: 0
Draws: 0
Goals conceded per game: 2
Win percentage: 0%

16. Joe Gomez and Joel Matip 
Goals conceded: 3
Games together: 2
Defeats: 0
Wins: 0
Draws: 2
Goals conceded per game: 1.5
Win percentage: 0%

15. Ozan Kabak and Jordan Henderson 
Goals conceded: 4
Games together: 3
Defeats: 2
Wins: 1
Draws: 0
Goals conceded per game: 1.3
Win percentage: 33.3%

14. Jordan Henderson and Fabinho 
Goals conceded: 5
Games together: 4
Defeats: 2
Wins: 0
Draws: 2
Goals conceded per game: 1.25
Win percentage: 0%

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13. Rhys Williams and Billy Koumetio
Goals conceded: 1
Games together: 1
Defeats: 0
Wins: 0
Draws: 1
Goals conceded per game: 1
Win percentage: 0%

12. Ozan Kabak and Nat Phillips
Goals conceded: 1
Games together: 1
Defeats: 1
Wins: 0
Draws: 0
Goals conceded per game: 1
Win percentage: 0%

11. Fabinho and Virgil van Dijk
Goals conceded: 2
Games together: 2
Defeats: 1
Wins: 1
Draws: 0
Goals conceded per game: 1
Win percentage: 50%

10. Jordan Henderson and Nat Phillips 
Goals conceded: 3
Games together: 3
Defeats: 1
Wins: 2
Draws: 0
Goals conceded per game: 1
Win percentage: 66.6%

9. Nat Phillips and Joe Gomez
Goals conceded: 1
Games together: 1
Defeats: 0
Wins: 1
Draws: 0
Goals conceded per game: 1
Win percentage: 100%

8. Rhys Williams and Fabinho 
Goals conceded: 4
Games together: 6
Defeats: 2
Wins: 3
Draws: 2
Goals conceded per game: 0.66
Win percentage: 50%

7. Nat Phillips and Fabinho
Goals conceded: 1
Games together: 2
Defeats: 0
Wins: 0
Draws: 2
Goals conceded per game: 0.5
Win percentage: 0%

6. Fabinho and Joe Gomez
Goals conceded: 1
Games together: 3
Defeats: 0
Wins: 3
Draws: 0
Goals conceded per game: 0.33
Win percentage: 100%

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5. Joel Matip and Fabinho
Goals conceded: 2
Games together: 6
Defeats: 1
Wins: 4
Draws: 2
Goals conceded per game: 0.33
Win percentage: 66.66%

4. Virgil van Dijk and Joel Matip
Goals conceded: 0
Games together: 1
Defeats: 0
Wins: 0
Draws: 1
Goals conceded per game: 0
Win percentage: 0%

3. Rhys Williams and Virgil van Dijk
Goals conceded: 0
Games together 2
Defeats: 0
Wins: 1
Draws: 1
Goals conceded per game: 0
Win percentage: 50%

2. Rhys Williams and Joe Gomez
Goals conceded: 0
Games together: 3
Defeats: 0
Wins: 2
Draws: 1
Goals conceded per game: 0
Win percentage: 66.66%

1. Jordan Henderson and Joel Matip
Goals conceded: 0
Games together: 1
Defeats: 0
Wins: 1
Draws: 0
Goals conceded per game: 0
Win percentage: 100%

We should add the obvious caveat that Van Dijk and Gomez's stats are skewed by the 7-2 defeat to Aston Villa, while some pairings have only featured in one game. 

Liverpool just haven't been fortunate enough to land upon a consistent partnership this season - and it goes a long way towards explaining why they're wrestling even for a top-four place, never mind the title.