Liverpool could have to face West Ham United on Saturday with only one senior center-back available to Jurgen Klopp after Fabinho's injury in their 2-0 win over Midtjjylland in the Champions League on Tuesday.
Fabinho limped out of the match at Anfield before halftime, having injured his hamstring without contact from an opposing player. The Brazilian, a more natural midfielder who has been redeployed at center-back in Virgil van Dijk's absence, was immediately withdrawn in favor of academy graduate Rhys Williams.
The 19-year-old could be asked to make his Premier League debut on Saturday alongside Joe Gomez with the outlook on Fabinho's injury seeming far from optimistic.
"We have to wait for the scan obviously but on these occasions," Klopp said after the game, "when somebody's going off with a muscle problem, it's pretty rare that the doc calls me the next morning and says 'ah, false alarm, all fine, he can go again.'
"It's now only about how long. That's all. Nowadays a week means three games, 10 days means four games, 14 days means seven games and all these kinds of things."
Klopp added that Fabinho had told him that he would not be able to sprint if he had continued in the game, which Liverpool won thanks to second-half goals from Diogo Jota and substitute Mohamed Salah.
Liverpool had entered the game with Joel Matip unavailable as he struggles to overcome the injuries that have plagued his career in England. Asked in his post-match press conference whether the Cameroon international could be available when his side face West Ham on Saturday, Klopp said: "I don't know. We have to see.
"If it was one game at the end of the season, we could probably make one or the other play. But we have a game three days later. The players need a proper build up."
The Reds had already been facing the task of playing out much of the remainder of this season without talismanic center-back Virgil van Dijk. The 29-year-old will undergo surgery on the anterior cruciate ligaments he damaged in the 2-2 draw with Everton earlier this month.
Liverpool have not set a timescale on Van Dijk's return but such injuries typically sideline players for at least six months.