They can't transfer his registration, yes. Sorry if I wasn't clear - did it make a difference to the point of the post?Thats not strictly true is it, they CAN sign him they just cant register / play him (like Barca summer before last who got Turan? who couldnt play for several months)?
Atleti probably dont want his wages on their books for that time admittedly (the difference in the suitable size of the fee is probably whats holding up the deal at a guess)