I think Mangala is much better than what he is showing but I do wonder whether he needs to protected more with maybe a more defensive system and less of a high line to show it.
I also think if Guardiola did come in I don't think Magala is good enough on the ball to play his style of football.
In regards to our academy lads, nobody knows yet how good they will turn out, even with Denayer we don't know how good he will be for City yet.
Stones for me has proven in the last 12/18 months that he is on his way to becoming the best English ball-playing defender since Ferdinand, he isn't perfect but you can see he is a player if top quality whom for me would get into any side in England.