Tolmie said that there is something to this, and that Mangala is mooted for a possible move the other way.
I know this would be an unpopular view, but it is conceivable that Txiki thinks that Otamendi is a better player than Mangala. The other relevant issue is the age of Demichelis, and Vinny's tendency to break down with injuries.
So it me I can see the sense to this, and if it meant Mangala going the other way then I personally wouldn't have a problem with that. I am stil not convinced that Mangala is the right player for our European adventures this season.