Martinez was reacting to some criticism from England coach Roy Hodgson of his young prospect.
"He is the biggest talent for his age I have seen in European football," he said.
"He is a special player, a unique player and that is so rare. He has power, pace and technical ability - elements you rarely find in a player. He would look at home in the Spanish, German or Dutch models, no doubt about it. We have a responsibility to develop his talent and to protect and nurture him."
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