Liverpool defender Dejan Lovren had to be removed from Tuesday's Champions League encounter with Red Bull Salzburg, dealing an injury blow to a defence already shorthanded.
In the second half of the Group E finale, the Croatia international took a knock to his knee and after receiving treatment on the pitch, he was unable to continue.
With Lovren limping off the pitch, Joe Gomez was introduced in his place in the 53rd minute at Red Bull Arena.
In a game the Reds desperately needed a result from, Lovren's exit was quickly followed by goals from Naby Keita in the 57th minute and Mohamed Salah a minute later.
Liverpool would win the contest 2-0, ensuring they finish first in Group E and advance to the round of 16 as they look to win the Champions League for a second straight season.
Speaking after the game, Liverpool manager Jurgen Klopp expressed optimism that Lovren's injury was similar to a cramp that knocked him out of last weekend's match against Bournemouth.
“We hope that it’s exactly the same as last time. He felt something and we made the decision. It’s of course not cool," Klopp said.
“He played really well and was very important. We don’t know more in the moment. It felt similar like last time, that’s it. We have to see.”
The Croatian's injury could have a serious impact on a Liverpool defence that has already been operating without Joel Matip since October.
The Cameroon international has been dealing with a knee injury and as Klopp revealed last weekend, he could be out until 2020.
“It was not like after four weeks or so that it was already as we wished, so we have to wait another two weeks I would think and then we will see," Klopp told Liverpool's official website.
“But then he will have been out for six weeks or so, if it is perfect, fine, but he might need to rebuild his physical things as well, which is not too cool, but it is nothing serious.
“It will be fine, but the problem is between now and then, we play 10 times and that is the situation.”
With Gomez and Virgil van Dijk the club's only experienced central defenders, the Reds face a difficult situation ahead of a busy period that will feature three seperate competitions.
Liverpool face Watford in Premier League action on Saturday before a Carabao Cup encounter with Aston Villa three days later.
Klopp's men will then travel to Qatar for the Club World Cup, where they will feature in a semi-final tie on December 18 before a possible final three days later.
