He's good but I'm not sure how do we plan to use him. Like I said previously, it's hard to define his position on the pitch. He's tireless and can be seen everywhere on the pitch, but this year he exploded and he did so because he was given a much more advanced and free role, which didn't limit him tactically. Maybe I'm slightly wrong, but on many matches I've seen he played almost the same role Hamsik plays for Napoli, which is way too attacking.
He was Levercusen's top scorer and top assist man in Bundesliga this year (10 goals and 11 assists) and the biggest reason why Levercusen finished 2nd.
Now, I know that he can play more defensively, but I really don't see how he'd fit in a 2 men CM. He fits perfectly in a 3 men midfield with Pirlo and someone with strictly defensive duties like Lass, but I can't imagine him in a 4-4-2 or a more attacking 4-2-4.