The Dutchman spent last season on-loan with Swansea City.
Agent Fabio Parisi told SportItalia: "At Napoli, they simply take players who can perform a function for them. They do not take players just for the sake to take them.
"(Coach) Rafa Benitez knows what he wants. De Guzman is flexible, can build a play, defend, he is a complete player.
"The right conditions have emerged for him to be signed. The talks are now advanced."
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