Martinez believes Barry is playing with the enthusiasm of a player who has only just started his football career.
"He is someone who breathes the game. He is playing with the enthusiasm and desire of an 18-year-old. We are enjoying having him here."
However, the Spaniard thinks it is too soon to look at signing Barry, on loan from Manchester City, on a permanent deal.
"I wouldn't think about starting that (talks over a move) yet. It is too early," said Martinez.
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