Liverpool goalkeeper Alisson is expected to be out until at least mid-November with a hamstring injury.
The Brazil international was hurt in the 1-0 win at Crystal Palace on Saturday and was replaced by Vitezslav Jaros after 79 minutes.
Liverpool do not expect Alisson to be back before the next international break, which takes place 11-19 November following a round of league games.
Prior to that, the Premier League leaders face top-flight matches against Chelsea, Arsenal, Brighton and Aston Villa, while they play RB Leipzig and Bayer Leverkusen in the Champions League and Brighton in the Carabao Cup.
Caoimhin Kelleher missed the game at Palace because of illness but is expected to replace Alisson in goal.
"It is quite clear then that he [Kelleher] is the number two," said Liverpool boss Arne Slot following the game at Selhurst Park.
"Otherwise, the last time Alisson was injured I would have played Vit, but I played Caoimhin. So Caoimhin is the number two and did really well."
Kelleher came in for Alisson when the 32-year-old had a spell out in September, playing in a league win against Bournemouth and League Cup victory against West Ham.
Liverpool's first game following the November international break is at Southampton on 24 November, before they then face Real Madrid, Manchester City, Newcastle United and local rivals Everton.
BBC Sport fan writer Jordan Chamberlain
In Caoimhin Kelleher, Liverpool have arguably the world's most impressive back-up keeper.
It almost felt unfair to keep him in the summer. He is 25 and obviously deserving of a starting spot in a Premier League side.
So while Alisson's injury is a blow, it does not fill me with worry.
It also makes Liverpool’s deal for Giorgi Mamardashvili in the summer make more sense.
The Georgian was an expensive signing, but a pretty unexciting one - given he went on loan to Valencia for the year and because he plays in Alisson's position.
Most Reds would prefer Alisson stay for the next five seasons, but his abnormal injury record for a keeper means we need an elite deputy.
Kelleher has fulfilled that role but he will not do it forever. He is too good.
Mamardashvili hopefully is too, but perhaps will be happy to learn from Alisson for one season before stepping up in 2026-27.
We asked for thoughts on how big a blow losing Alisson is for the Reds on our dedicated Liverpool page. Here is a selection of the comments:
Natalie: Alisson was injured in November last year and in February 2024. By the time he came back full-time, we had won the Carabao Cup and were still in the Europa League and FA Cup. Kelleher is an excellent keeper. We still have a great defence. We'll be fine.
Fraser: Losing Alisson just before our difficult run is a blow. He's very unfortunate to get injured so many times. That being said, it's not a fatal blow. We are lucky to have Kelleher as a solid back-up and this is his time to shine.
Ken: While Alisson arguably is a world-class goalie, he is also world class at picking up injuries. I cannot recall a keeper being so injury prone, which brings into focus the reasons for the acquisition of Mamardashvili from next season. However, at present, Kelleher will be a more than able deputy, as he has been in recent seasons.
Rybr: It's not that big an issue, which is a strange thing to say when you're talking about the greatest keeper in the world. Liverpool's number two is probably the fourth-best keeper in the league so the drop-off is minimal.
Janet: Gutted for Ali. He's been in good form and saved us at times this season already. He's been a key part in our defensive solidity. I just hope he's not rushed back and is allowed to properly heal.