Liverpool midfielder Philippe Coutinho could be out for the rest of January after injuring a hamstring in the League Cup win against Stoke.
Defender Dejan Lovren also suffered a similar injury and Kolo Toure cramp, but both have shorter recovery times.
The Reds face Exeter in the FA Cup third round on Friday (19:55 GMT).
"Phil's is more serious than Dejan and Kolo but none of these players will be available on Friday," said manager Jurgen Klopp.
Liverpool's January fixtures
8 Jan: FA Cup third round - Exeter (a)
13 Jan: Premier League - Arsenal (h)
17 Jan: Premier League - Man Utd (h)
23 Jan: Premier League - Norwich (a)
26 Jan: League Cup semi-final - Stoke (h)
"Kolo should be available next week, Dejan will be available after Manchester United. Phil needs one or two weeks longer."
Six Reds players - Coutinho, Lovren, Martin Skrtel, Jordan Rossiter, Divock Origi and Daniel Sturridge - are out with hamstring injuries.
And with Mamadou Sakho also sidelined, the Reds do not have a senior central defender available to face Exeter.