Stones impressed in their FA Cup win over QPR on Saturday.
"I really thought I'd got him (as Wigan Athletic manager), on deadline day last January, and was really disappointed when he chose Everton, because I knew what a special talent he was," said Everton boss Martinez. "He is so composed, and defensively he has got everything. He knows he is stronger, quicker and more athletic than the striker he is marking, and that gives him real confidence.
"We play him in a back three to allow him to understand the concept of a centre half. He is ready to play in a back two as well, and he has an incredible future.
"I think he will develop and become a special centre half for England."
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