Liverpool centre-back Virgil van Dijk needs surgery after picking up a knee-ligament injury during the derby draw with Everton on Saturday.
The club have confirmed that Van Dijk suffered anterior cruciate knee ligament damage and will go under the surgeon's knife. He will face a fight to play again this season.
Van Dijk was hurt in a reckless challenge by Everton keeper Jordan Pickford in the first half of the 2-2 draw at Goodison Park.
After the match, Liverpool manager Jurgen Klopp questioned why no action was taken against Pickford.
"For me it was a clear penalty that I saw. Then obviously we saw the flag went up, so offside. I still thought it was worth a look on the foul but that didn't happen," said Klopp.
The club did not specify a timescale for the 29-year-old defender's return to action.
Van Dijk has been pivotal to Liverpool's resurgence under Jurgen Klopp since making a then world record £75 million ($96.9m) move for a defender from Southampton in January 2018.
The 29-year-old has started every league game for the past two seasons as the Reds won the Champions League in 2019 and ended a 30-year wait to win a league title earlier this year.
"Virgil played for us I don't know how many games in a row. He plays with pain, he plays with pretty much everything, but he couldn't play on. That's not good," said Klopp.
Van Dijk's absence is compounded by goalkeeper Alisson Becker also being sidelined by a shoulder injury.
Without the Brazilian in goal, Klopp's men have conceded nine times in their last two matches, including a historic 7-2 humiliation as Aston Villa two weeks ago.