His development under pep hasn't been as good as I expected.
Good on the ball but abysmal at everything else. However he's young and will in time improve but City seriously lack a real leader in the back line as Kompany is made out of glass and can't stay fit for long stretches of time.
Pep wants Stones to be his new Pique but without a proper defensive partner (like a Puyol) to call Stones out for his mistakes and help get the kid on the right path it's not going to happen. Pique when he came here had the likes of Puyol,Marquez,Milto,Abidal etc to learn off of in his first season which helped him out immensely down the line.
Seems like Pep is constantly changing the back line tactics and throwing the kid in there expecting him to defend and pass the ball.