Liverpool captain Jordan Henderson has undergone an operation on the groin injury he sustained in last weekend's Merseyside derby defeat against Everton.
The midfielder, who has been deputising in Liverpool's injury-ravaged defence, will miss at least five games as the club rule him out until April at the earliest.
Henderson was forced off half an hour into the Toffees' win and further investigation by the club's medical team led to the England international having an operation.
Manager Jurgen Klopp remains hopeful Henderson will play again this season.
"The best-case scenario, I don't know. It's not a quick one but we hope there is still a possibility for him to play a few games this season," he said.
He has received some good news as, after Diogo Jota trained this week following three months out with a knee problem, Fabinho and fellow midfielder James Milner are set to return to training on Saturday.
However, he admits they have not yet considered Alisson Becker's availability for Sheffield United on Sunday after the goalkeeper's father died in a swimming accident in Brazil on Wednesday.
"No comment about that. There's nothing to say. We didn't think about that (him playing this weekend)," he added.
"Diogo has trained twice with the team and looked really good but he's been a long time out. Fab will have his first session back with the team tomorrow. The same with James (Milner)."
In a statement the club said Henderson has undergone a successful procedure on his abductor.
"No specific timescale is being placed upon his return; however, the 30-year-old is ruled out initially until after the March international break."
The midfielder's return to full training will be dependent on how his rehabilitation progresses.
Liverpool play Sheffield United, Chelsea and Fulham in the Premier League, before the second leg of their Champions League tie with Leipzig and a trip to Wolves before the international break.
Liverpool are away to Arsenal on 3 April in their first game after the international window, with Henderson unlikely to feature for England in their 2022 World Cup qualifiers against San Marino, Albania and Poland.
Henderson, who has been playing as an emergency centre-back, joins an injury list which has showed no signs of shrinking for manager Jurgen Klopp this season.
His three senior central defenders Virgil Van Dijk and Joe Gomez (both knee) and Joel Matip (ankle) have all had their seasons ended prematurely, while back-up Fabinho is still out having played just one of the last seven matches because of a muscle injury.
James Milner is still sidelined by a hamstring problem, fellow midfielder Naby Keita only returned to the squad last weekend for the first time since mid-December while forward Diogo Jota began full training this week after three months out with a knee problem.