Liverpool captain Jordan Henderson will be sidelined for up to three weeks after suffering a hamstring injury against Atletico Madrid, the Premier League leaders announced on Friday.
Henderson picked up the injury towards the end of the 1-0 defeat to the Spanish side in the Champions League last-16 first leg on Tuesday.
The England midfielder has been assessed by Liverpool's medical team and was seen leaving hospital after scans on Friday.
Liverpool manager Jurgen Klopp revealed the time-frame for Henderson's recovery at Friday's press conference ahead of Monday's Premier League clash with West Ham.
"We heard of different hamstring injuries now around in the Premier League, Harry Kane, for example," said Klopp. "It's not that bad.
"But he will be out, I think, for three weeks or so, which is not cool. But how we see it, we were still lucky. That's it."
Henderson's injury is a blow to Liverpool as he is one of the team's most influential players.
The 29-year-old was recently made favourite by bookmakers to be crowned players' player of the year.
Klopp does have options to cover for Henderson, with Naby Keita back from injury and Alex Oxlade-Chamberlain in good form.
Henderson's absence also comes at a time when champions-elect Liverpool, 22 points clear at the top, face a run of relatively undemanding league fixtures against West Ham, Watford and Bournemouth.
There is also an FA Cup fifth-round tie at Chelsea to come on March 3 and Klopp will hope Henderson can make a quick recovery in time for the second leg of the Champions League tie against Atletico at Anfield on March 11.
The Champions League loss at the Estadio Metropolitano was only Liverpool's third defeat of a remarkable season and Klopp expects an immediate response against West Ham.
The lowly Hammers could be ideal opponents for Liverpool, on a run of 17 successive league wins, as they look to move a step closer to a first English title since 1990.
"We lost the game, there's absolutely no positive in it, but if there's any help in that result it's that you felt a defeat," Klopp said.
"Nobody thought: 'Oh, in the league we're fine'. We have to put it right to get the other feeling back. I don't think we ever lost how a win feels, but now we lost the difference is massive.
"It's much more than three points. It's really from sunshine to hardest rain. That's how it should be if you want to be successful.
"Then it has to feel really bad and that's how it felt. So yes, we want to put it right even though it will be a different competition."
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