Heres my thinking...
United are our biggest threat to the title this year.
Next week Arsenal play united.
Could a deal have been done to keep nasri out of arsenal champs league games, but play him in premier league (including united game). this gives the gooners more chance of taking a point (points) out of that game, and also suits them as they are short on experience in the midfield & defence at the moment.
After the United game (provided Nasri is injury free) we than complete the deal to sign him. Meaning he has had a chance already to take points from some of our rival (Liverpool and Utd) albeit Arse where shite yesterday.
And we get him in time for our CL campaign starting.
Whilst all this is happening Arsenal fans live in hope that he is in fact staying.