Matt the Giant said:
Apparently that was a condition set by Ac Milan, both of them or no deal. They must really need the money (to buy Tevez to start with I hope!)
As I see it, Thiago Silva and Ibra are the only two world class players left at Milan. I believe the situation is that if one of them goes, the other one will lose any faith they have left in the Milan project, so if one goes, the other is gone as well.
Having said that, there are different scenarios: one of PSG and City could get both, but it could end with PSG signing one of them and we sign the other one.
I think there's a lot of truth to this, a month ago Thiago Silva was only a signature away from becoming a PSG player, but for a Kaká-esque (and Pato-esque) last-minute "change of heart" from Milan.