And the midfielder has thrived since arriving at the Emirates, impressing even keen admirer Klopp.
He told TV2: "I really like him. It's easy these days. It was a bit more difficult at the start of his career when he was at Real Madrid. Then it looked like it might not go his way.
"I was really disappointed by that, because we wanted him in Dortmund when he was very young.
“We had a long conversation when he was still a boy, together with his father. In the end he decided on Madrid, and that's fine, but that's why I've always followed him."