If we can't offer CL football I don't think he'd want to come here over staying at Athletico. And that's not even factoring in other suitors, if he is available.
The guy has just broken through at a highly promising team under one of the best managers in the world. Yes, Athletico are, in terms of club stature, nothing compared to us. But they're far more likely to be in the CL next season, or to win it for that matter (not that I think they will, but they've a better chance than us). Add that he'd be leaving his country to come here, plus a dash of reservations regarding our manager...It's not a particularly enticing offer is it?
The only thing we can really offer over Athletico right now is higher wages. Given his young age, that probably will not be enough to sway him against all the aforementioned factors.