The 23-year-old defender, capped 11 times by Argentina, welcomed a chance to play in Spain.
"The Spanish league is very competitive," he said at a press conference. "It is true that Real Madrid and Barcelona have the advantage in the league, but there is a great quality of players and this is the best league in the world, no doubt."
Despite breaking through at international level, Fernandez has struggled for playing time in Naples.
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