Joe Gomez had completed successful surgery on a patella tendon injury, as his season now hangs in the balance.
Liverpool confirmed on Thursday that the defender had the surgery, after scans showed a rupture to the tendon, following a knee injury sustained training with England.
The club also – importantly – revealed that Gomez suffered no ligament damage in the training ground accident, which happened when no other player was near him. They are not yet ruling out a return this season.
It is understood the surgery was carried out swiftly to offer a better hope of a successful repair to the damaged tendon, and avoid scarring which could add complications to the recovery.
He will now undergo a programme of rehabilitation which usually would take up to six months, as the player will be immobilised for around eight to 12 weeks, to help the tendon rejoin.
Liverpool have put no timescale on his recovery, but it is understood they are not yet ruling out a return by the end of the season.
Such a timescale would depend on leg strength in the recovery, but if the rupture in the ligament has been repaired without issue, then it is possible he could be back running within three months, allowing a potential return before May.
It is yet another blow to manager Jurgen Klopp though, who has lost centre half Virgil van Dijk for the season with cruciate ligament injury.
England defender Trent Alexander-Arnold is also out with a calf injury, and could be out for up to a month, though Liverpool are hopeful of a return soon after the international break.
Stand in defender Fabinho suffered a hamstring problem, but he is expected to be back in contention after the international break.
It leaves Klopp with only one fit senior centre half in Joel Matip – who has suffered serious injury problems of his own over the past two years – and makes it now seem certain he will dip into the transfer market to buy an experienced centre half in January.