Jose Mourinho has explained that Eric Bailly has been dropped for recent Manchester United games because his "country is not in the World Cup," so he wants to give his other centre-backs the best chance of being picked for their national team squads this summer.
Bailly will not be going to the 2018 FIFA World Cup this summer with the Ivory Coast as they could only finish second to Morocco in Group C of CAF qualifying.
United's other four centre-backs—English duo Chris Smalling and Phil Jones, Argentinian Marcos Rojo and Swede Victor Lindelof—could all go to Russia if they are selected for their national teams.