Virgil van Dijk has undergone successful knee surgery and will begin rehabilitation, Premier League champions Liverpool said on Friday.
The club did not say for how long the 29-year-old central defender would be out.
Van Dijk, who was pivotal in both Liverpool's Champions League success in 2019 and their title triumph last season, suffered cruciate ligament damage after a tackle from Everton goalkeeper Jordan Pickford earlier this month.
"Virgil van Dijk has undergone surgery on the knee ligament injury he sustained earlier this month," read a club statement.
"The Liverpool defender's planned operation took place in London and was conducted successfully.
"Van Dijk will now immediately focus on the beginning of his rehabilitation with the support of the Reds' medical department.
"No timeframe has been placed on the Dutchman's return to action."
Reds coach Jurgen Klopp, at his press conference on the eve of their Premier League home game with West Ham, said Van Dijk was doing okay.
"This time (after a operation) is always unpleasant. He is good as good as can be," said Klopp.
The Dutch international's absence adds to Liverpool's problems in central defence.
Joel Matip has missed the last three games injured and makeshift centreback Fabinho limped off in the first half of Tuesday's Champions League win over Midtjylland with what is believed to be hamstring injury.
"Fab (Fabinho) is not in, he has a little injury," said Klopp.
"He's out for the weekend and slightly longer but all the others are in contention."
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)