Too much pessimism in this thread. Ake is a much better option than Stones, Otamendi or Garcia (for now at least). At this stage, I'd be happy just to have a reliable premier league centre-back who isn't error-prone.
The number of mistakes made by Stones and Otamendi, this season in particular, is a bit of a joke. It can't just be down to the way we play - it's like a collective brainfart every time we face a counter attack.
Ake is a great player, and could mature into another leader at the back for us. Think we'll get him and maybe Alaba, who can also play CB. That should give us enough cover, with Garcia having some room to grow.