Liverpool defender Joe Gomez has had surgery on a knee injury and is "likely" to miss a "significant part" of the rest of season, the club says.
Gomez was injured on Wednesday while training with England before Thursday's friendly with the Republic of Ireland.
The 23-year-old's club said he had undergone "successful" surgery to repair a tendon in his left knee.
The Reds are already without fellow centre-back Virgil van Dijk because of a long-term knee ligament injury.
"The issue was isolated to Gomez's tendon, with no damage to any other associated knee ligaments," Liverpool said.
"No timescale is being placed upon his return, though the issue is likely to rule him out for a significant part of the remainder of 2020-21."
Gomez has played in all but one of Liverpool's Premier League and Champions League games this season.
The injury is not the same as the cruciate ligament injury he suffered in 2015.
Van Dijk has had surgery on the knee ligament injury he picked up against Everton in a 2-2 draw on 17 October.
The Premier League champions have also been without Fabinho, who had been deputising in defence for Van Dijk, because of a hamstring injury.
Additionally, Liverpool have an injury concern over right-back Trent Alexander-Arnold, who was taken off during the 1-1 draw at Manchester City on Sunday and withdrawn from England duty.