Liverpool have confirmed that Virgil van Dijk has undergone surgery on the knee ligament injury he sustained earlier this month.
The Dutch defender suffered the injury during the Merseyside derby earlier this month following a challenge from Everton goalkeeper Jordan Pickford.
Liverpool say Van Dijk's planned operation took place in London and "was conducted successfully".
The 29-year-old will start his rehabilitation but the club say no timeframe has been placed on his return to action.
.@VirgilvDijk has undergone successful surgery on the knee ligament injury he sustained earlier this month.
He'll now focus on the beginning of his rehabilitation with the support of our medical department 💪
— Liverpool FC (@LFC) October 30, 2020
Jurgen Klopp will also be without Fabinho for the next three games due to a hamstring injury he picked up in the Champions League win over FC Midtjylland on Tuesday night.
The Premier League champions could hand teenager Rhys Williams a first top flight start against West Ham at Anfield on Saturday.
Captain Jordan Henderson may also be asked to play in central defence as he did in the Club World Cup semi-final against Monterrey last year.
Meanwhile, West Ham will be without Michail Antonio for their trip to Anfield due to a hamstring injury.
The 30-year-old forward has been in impressive form and scored a stunning overhead kick in the 1-1 draw against Manchester City last weekend.
Antonio was forced off early in the second half of that game with a tight hamstring and Hammers boss David Moyes has confirmed he'll be without his talisman.
West Ham ran Liverpool close at Anfield last season before goals from Mo Salah and Sadio Mane turned it around in a 3-2 win for the Reds.