Jurgen Klopp has confirmed Naby Keita will miss Sunday's FA Cup clash with Merseyside rivals Everton due to a groin injury he suffered before Thursday's 2-0 win over Sheffield United.
Keita was initially named in the starting XI to face the Blades in the Premier League, but a problem sustained in the warm-up forced him to miss out, with James Milner taking his place in the midfield.
It is the latest in a long list of niggling fitness problems the Guinea midfielder has had to endure since moving from RB Leipzig, and the 24-year-old has only made five Premier League appearances this term.
He now appears set for another spell on the sidelines, though Klopp was uncertain of the severity of the injury or even how it was sustained.
"I don't know exactly what he has – it was the groin – but I can say already he will not be involved against Everton," Klopp told reporters.
"That makes it 12 adult players we have [available], plus the kids, so that's not cool, but we cannot change it.
"I have no clue how it happened, I think it was the last shot in the warm-up when he felt something. He came in [the dressing room] and was limping.
"Everybody who has played football has had this kind of injury and it's not nice, it's painful. I don't know exactly what it is or how long it will take, but I can say already he will not be ready for Sunday."
After Sunday's Merseyside derby, Liverpool are next in Premier League action on January 11 at Tottenham.