Liverpool defender Joel Matip could be out for up to six weeks as he needs surgery on a fractured collarbone suffered in the 1-0 win against Napoli.
The 27-year-old landed awkwardly in the closing stages of Tuesday's Champions League game and was taken to hospital.
Liverpool are already without defender Joe Gomez, who fractured his leg against Burnley last week.
The Premier League leaders reached the last 16 of the Champions League with the win against Napoli.
They will already be without Matip's central defensive partner Virgil van Dijk for their next Champions League game, in mid-February, because of suspension.