Stones biggest problem is who he has next to him. He's still learning his trade and as such should be paired with an experienced older head who can point him in the right direction. Instead he has Otamendi, who is frequently out of position or makes a rash challenge and gets turned, leaving Stones to deal with the aftermath. Quite often you will see Stones shouting instructions to Otamendi when he should actually be getting them.
The talent is clearly there and I am still hopeful it will shine through, it won't with clowns like Otamendi next to him though.