Liverpool will be without Joel Matip for up to six weeks as the defender is set for an operation on a fractured collarbone.
The centre-back was taken to hospital after suffering the injury in the late stages of Tuesday's 1-0 win over Napoli in the Champions League.
And Liverpool have now confirmed Matip, 27, will need surgery to fix the bone and will be out of action for several weeks.
"Matip was taken to hospital following the fixture and further assessment deemed an operation is required," a statement on the club's website read.
"Early indications suggest the centre-back is facing a spell of up to six weeks out of action, though that is dependent on how Matip responses to his treatment and rehabilitation programmes."
As well as missing Sunday's Premier League encounter with Manchester United, the Cameroon international will be forced to sit out of his side's meetings with Arsenal and Manchester City.
Matip has been used sparingly by Jurgen Klopp this season, but the crucial clash at Anfield was his third start in a row for the Reds, who progressed to the knockout rounds of the Champions League with the victory over Napoli.
Klopp's men also suffered injuries to Trent Alexander-Arnold, who needed to be replaced by Dejan Lovren in the 90th minute, while James Milner also had to go off five minutes from time.
“Trent got a knock on his foot, we are not sure about what exactly it is. It is painful," Klopp told reporters after the game. “[Milner] had cramps. I hope it was only cramp. That was it, I don’t know anything else.”
The news of another defensive injury comes shortly after Joe Gomez was found to have fractured a bone in his leg during his side's 3-1 win over Burnley and ruled out for the rest of 2018.
Klopp's team are thin on centre-backs heading into the busy Christmas and New Year period, with Lovren and Virgil van Dijk the only fit options left.
They are top of the Premier League and unbeaten after 16 matches, holding a one-point lead over reigning champions Manchester City.