Arda Guler should leave Real Madrid, he cannot be a starter in this team. There are too many big name players in Real Madrid that cannot be benched for him to play. Even if they have bad performances, they will still start in the next game. Real Madrid is a big club and Arsa may want to take his chances there and fight for his spot. I think Arda can decide what’s best for himself.
He was never going to be a starter there, he knew about it t before he signed the contract, he's only a prosper and not a crucial member of the team. The best solution would be to go on loan for to mid table team with less pressure to get more playing time to help his development. He's not going to achieve that on the bench week in, weeks out.