"The Guinean Football Federation has reported today [Monday] that Naby Keita is set to miss their forthcoming fixtures due to a knee complaint," Liverpool said in a statement.
Guinea are set to face South Africa on Friday and Zambia four days later.
Liverpool also confirmed defender Trent Alexander-Arnold had pulled out of the England squad for matches against Switzerland and Ivory Coast due to a hamstring issue sustained ahead of the game against Forest.
Manager Jurgen Klopp had said on Friday that the problem would keep Alexander-Arnold out for a few weeks.
The club are also sweating on the fitness of forward Mohamed Salah, who is still feeling the effects of a foot injury that he picked up in a league match against Brighton & Hove Albion earlier this month.