#1 Sergi Samper

This player has been heralded as Sergio Busquets' heir for a few seasons now but it's not materialized yet. A defensive midfielder of similar height and style, Samper hasn't made the step up to the first team like Busquets had by this age. He has gone out on successive loans, to Granada and Las Palmas respectively, without impressing extensively.
Busquets has also been at his finest this season and looks to have many more years at the highest level left, meaning Samper's direct route to the first team is blocked for the foreseeable future.
At 23, the player should be looking for another La Liga club, on a permanent basis, to see his career hopefully flourish. The talent is there, he just needs the platform to prove it.