Joel Matip was forced off with an injury during the second half of Liverpool's 1-1 draw against West Brom, with selection problems in defence mounting for manager Jurgen Klopp.
The centre-back, who started alongside Fabinho against the Baggies, went down clutching his groin in the 58th minute at Anfield on Sunday and was replaced by Rhys Williams.
Klopp's squad is stretched with Williams, Nathanial Phillips and Sepp van den Berg now the only recognised central defenders he has available for selection.
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Senior centre-backs Virgil van Dijk (ACL) and Joe Gomez (tendon) are both sidelined with long-term knee injuries.
On Matip being forced to leave the field during the second half, Klopp said in his post-match press conference: "Joel told me he felt something in his abductor and that's obviously not too good.
"Not sure how serious it is now, but it was serious enough that he had to leave the pitch. The rest of the information I will get tomorrow.
"That's not the first time a centre-half is injured, so of course it's not good especially now when he was in really good shape again.
"But we cannot change that and we have to just accept it and carry on."
Liverpool led through Sadio Mane's first-half strike but Semi Ajayi's equaliser eight minutes from time ensured Sam Allardyce's men left Anfield with a point.
The Reds hold a three-point lead over Everton at the top of the Premier League following the draw over Allardyce's side
Carra: Liverpool must sign a defender in January
Sky Sports pundit and former Liverpool defender Jamie Carragher is adamant the club must sign a centre-back in next month's transfer window in order to bolster their options at the back for the second half of the season.
"It is a massive worry but it is not a new worry," Carragher told Sky Sports after Liverpool's draw with West Brom.
"That is why it is paramount Liverpool sign someone in January. I said that as soon as Virgil van Dijk had his injury. Fabinho has looked like a top-class centre-back, but Matip is just too injury prone. His body just can't take the rigours of playing in the Premier League week in, week out.
"I still believe Liverpool are the best team in the league even without Van Dijk. The only way they don't win it is if they have problems at centre-back where Rhys Williams or Nat Phillips have to play for a prolonged period. It's not a position for young players. At times they will make mistakes because they are young and learning.
"Liverpool need someone there to make sure that they don't end up with two young lads playing there for five or six weeks if, say, Fabinho went down injured.
"They have to do something in January."