He's spent few years here, his teammates like him, it's literally the best surrounding he can get, and his problem has always been his lack of effort, so I really doubt going to Sevilla will help him a lot. He is not a kid anymore.
His problem has always been mentally, and his lack of effort, I don't see how letting him go far away where we won't have any control over him will make him better player.
Give me one example where well run club lets player under their contract in similar situation go on a loan?