Liverpool have confirmed centre-back Joel Matip has been withdrawn from selection as the club seeks clarification over his availability for Premier League action.
Matip was not selected for Cameroon's squad for the Africa Cup of Nations - which got under way in Gabon on Saturday - and his last appearance for his country was in September 2015.
The centre-back previously indicated he did not want to be considered for international matches, but Liverpool said in a statement they are waiting for FIFA to confirm his club eligibility.
"The Cameroon Football Federation have failed to confirm that Matip can therefore play club football during the period of the Africa Cup of Nations," Liverpool's statement read.
"Liverpool have subsequently repeatedly sought, as a matter of urgency, clarity from FIFA in this regard. This includes assurances the player was called up for the tournament in accordance with the world governing body's regulations.
"It is Liverpool's view that the player should be available for club football during the period of the competition and will continue to work for a speedy and unambiguous resolution."
Trent Alexander-Arnold has been selected to make his Premier League debut in the absence of Matip and the injured Nathaniel Clyne, while Philippe Coutinho is on the bench as he continues his return from an ankle problem.
Liverpool XI to face Manchester United: Mignolet, Alexander-Arnold, Lovren, Klavan, Milner, Henderson, Can, Wijnaldum, Lallana, Firmino, Origi.