Speaking before the encounter in Greece, the Portuguese tactician stressed that leadership requires versatility and prioritising collective success over individual preferences.
With defensive absences limiting his options, Mourinho insisted Valverde must be willing to operate outside his preferred position.
"I see Fede as an extremely important player for the team," he told the media.
"The fact of being Real Madrid's captain makes him look around in a different way. When you are the captain, you have to be different.
“It is a responsibility and I think that will make him play wherever is necessary for his team and for his teammates.
“That is what a captain is to me and that is why I am convinced it will not be a problem for Fede to play wherever. If needed at left-back, he will do it because of the responsibility of a captain.”