Loaning him out to a La Liga club for one season is exactly the kind of planning you want for the squad. Then Pique and Umtiti are first choice, Vermalen backup and a youngster as 4th. Ideal, imo. Then after next season we can assess Marlons development, bring in a new young defender and let Mina take Vermaelens minutes, as Pique will need more rest at that time.