Liverpool striker Divock Origi has had a minor knee operation and will be out for the rest of the month, sources have told ESPN FC.
The sources said Origi had undergone surgery in his native Belgium at the end of December and would be sidelined for four weeks.
The news is an unexpected blow for the Reds, who take on Arsenal at Anfield on Wednesday, with Origi originally having been ruled out with a minor hamstring strain.
The 20-year-old was substituted in the first half of Liverpool's 1-0 Boxing Day victory over Leicester and replaced by compatriot Christian Benteke.
Origi is one of seven Anfield players currently suffering a hamstring problem, but had also been troubled by an ongoing knee issue and returned home for the operation.
His extended absence further reduces manager Jurgen Klopp's options in attack, with Danny Ings sidelined for the rest of the season, Daniel Sturridge unavailable and Philippe Coutinho out until February with a hamstring injury.
In defence, the Merseysiders have signed Steven Caulker on loan from Queens Park Rangers for the rest of the season after his previous loan spell at Southampton was cancelled.