His £40m valuation in the summer is now irrelevant.
His current "market value" is whatever we can get for him.
I'm not convinced we can sell him for a "reduced" fee of £20m then try to sue the player for any perceived shortfall. It would be nice to think it could happen, but I very much doubt it.
The fact Tevez has spent the last 8 or 9 weeks in Argentina with no disciplinary action taken against him would suggest that City know they have limitations in what they can do.
The nightmare scenario is that Milan fail to come up with a deal, and Tevez decides to just sit it out for the rest of his contract picking up £25m without any benefit for us.