Pedri spent last season on-loan with the Segunda Division outfit, having been signed last year.
Rios said, "He is one of those footballers who you immediately see the potential he has. As he surrounds himself with colleagues with a high level, he will increase this. He is very young and I am convinced that he is one of those players who are going to mark an era.
"He is a very complete boy. He has a weak physical appearance, but it is very difficult to take the ball from him. And in the place where he has fallen, at Barça, which has that perspective of keeping the ball and looking for those spaces, that is perfect. I was convinced that he was going to stand out and he has only just begun."