Liverpool confirmed a day later that the centre-back had to undergo surgery to fix a tendon in his left knee.
Manager Jurgen Klopp is without two members of his first-choice back four for the foreseeable future with Virgil van Dijk and Joe Gomez sidelined due to knee injuries while Fabinho, who was deputising in central defence, is also missing.
Meanwhile the champions will take on log-leaders Leicester City this weekend at Anfield.
"Of course, Liverpool, the whole squad is very good".
After the two-week global break, Liverpool will be back in Premier League action when they host table-toppers Leicester City in a marquee top-of-the-table clash and Jurgen Klopp has been boosted by the return to fitness of key players including Fabinho and Andrew Robertson. His options in midfield will be limited further if Henderson is ruled out as Fabinho is certain to miss the game with a thigh injury while Thiago Alcantara is also a major doubt due to a knee problem and Alex Oxlade-Chamberlain remains a long-term absentee.
"A cruciate ligament injury is sort of five to six months if everything goes perfectly. It's a huge blow".
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The Ballon d'Or victor explained: "I have no doubts if these players were fit, then Liverpool are the best team in the land".
The former Arsenal man grabbed an assist in Liverpool's final Premier League game of the 2019/20 season in a 3-1 win over Newcastle on July 26th.
"This has now thrown it up in the air a little bit".
After eight games of the Premier League campaign, the 27-year-old looks to be nearing a return to action after being spotted polishing his technique in training.