No, you're wrong.
For Madrid to sell Drenthe, Drenthe must agree.
Drenthe is probably seeing out his contract, so Madrid have loaned him out, in order to get him out of the way, or offload his wages, or what ever the reason is.
We can't sign him permanently, because he is still Madrids property.
In 6 months of his Madrid contract ending, he can sign a pre-contract with us, which is not legally binding that I'm aware of, should he want to.