After seeing john stones preseason was really impressed with him especially against juve, having to play up against the powerful llorente and tevez. Don't get much harder than that.
However if you are defending a a lead against both Chelsea and Newcastle you would naturally think that heitinga would be the first choice to come in with his experience. Under moyes no doubt it would have been the case.
It's the one thing that has impressed me Martinez, his faith to play youngsters such as Barkley and stones. It must give them a great deal of confidence knowing if I'm good enough age means nothing.