Liverpool are still assessing the extent of Fabinho's hamstring injury after initial scans.
The Brazilian pulled up and had to be substituted less than half an hour into the 2-0 win against Midtjylland at Anfield on Tuesday night.
He has recently been filling in at centre-back in the absence of Virgil van Dijk.
And a significant spell on the sidelines would deplete Jurgen Klopp's options even further in that department.
But the ECHO understands a time frame is yet to become clear as the injury continues to be looked at.
Klopp is expected to give the latest update at his press conference tomorrow ahead of the West Ham game at 5.30pm on Saturday.
Young defender Rhys Williams impressed from the bench in the Champions League and could be in line for more minutes.
It looks highly unlikely at this stage that Fabinho will feature in any of the matches before the international break.
Liverpool will be hoping that the 27-year-old has avoided a more serious "grade three" tear to his right hamstring.
Sign up to our free LFC newsletter
Get all the latest Liverpool breaking news, team news, transfer rumours, injury updates plus analysis of what's next for the Reds.
You'll also get the latest transfer talk and analysis straight to your inbox every day with our FREE email newsletter.
Lower grade damage will improve his chances of a quicker comeback.
But even a high "grade two" hamstring tear can potentially see a player missing for four to six weeks, depending on recovery progress.
After the Hammers this weekend, Liverpool have a crunch clash against Atalanta in the Champions League next Tuesday and return to domestic action away to Manchester City five days later.
*Who do you want to see at centre-back against West Ham? Have your say in the comments section.
In the final 10 days of November, the Reds then take on Leicester City, Atalanta and Brighton.
Klopp will want Fabinho firmly back in the mix to bolster his defence ahead of a busy December which sees the Reds play eight games in 28 days.
