Liverpool defender Virgil van Dijk has had a "successful" operation on his knee ligament injury, the club say.
The 29-year-old has not played since damaging anterior cruciate ligaments (ACL) in a challenge with Everton goalkeeper Jordan Pickford in the 2-2 Premier League draw on 17 October.
Liverpool said "no timeframe has been placed" on Van Dijk's return.
"This time [after an operation] is always unpleasant. He is good as good as can be," said manager Jurgen Klopp.
"The surgery was successful, which is really good, the best news we could get."
Returning to action after ACL surgery can take several months.
Liverpool have since lost Fabinho, who had been deputising in defence for Netherlands international Van Dijk, to a hamstring injury.
Klopp said Brazilian Fabinho will miss Saturday's league game against West Ham "and probably slightly longer".
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