Martyn says that as an experienced goalkeeper it is crucial to nurture central defensive talent such as Stones - a situation he found himself in with the up and coming Jonathan Woodgate at Leeds United several years ago.
"Like Tim [Howard] with John Stones, I had that with a very young Jonathan Woodgate at Leeds," Martyn told evertonfc.com. "We had a senior back four at the time with Lucas Radebe and David Wetherall but Jonathan broke into the team when he was very young.
"He was quick which helps because if he did make a mistake he can overturn those errors. But if they are keen to learn, a few helpful hints from behind from us goalkeepers can usually get them in the right place.
"But if they have got the quality, they will make the grade."
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