I never understood the idea that a defender "always has a mistake in him", surely they all do?
Umtiti, Ramos, Walker, Boateng, Toby et al, have all made mistakes that have led up to a goal in this tournament alone - but they aren't what is typically described as players with a "mistake in them"
It just seems like a cop out to describe certain players, while conveniently ignoring other defenders who have a better reputation, but still make mistakes.
That being said, I don't rate Stones that highly.