Former Real Madrid goalkeeper Diego Lopez believes Julen Lopetegui has a plan for Thibaut Courtois and Keylor Navas.
Keylor was back between the posts for the Champions League win over AS Roma.
Lopez, now with Espanyol, told AS: "Who must start? I do not know, they are two great goalkeepers. Moreover, it has become commonplace, since many teams have two high level goalkeepers.
"The final decision lies with the coach, who is always looking for the best solution for the team. Anyone can start, but Lopetegui is not stupid, he will choose the best for all three competitions."