Relegation from the top flight is expected to signal an exodus of the Spanish club's stars, with Cristian Zapata and Giuseppe Rossi expected to follow in Valero's footsteps for an exit.
A statement on the Italian team's official website read: "Villarreal and Fiorentina confirm they have reached an agreement for the outright transfer of the player Borja Valero.
"This will be subject to the signing of the player's contract."
Valero's only experience abroad was with English Premier League outfit West Brom in 2008. He subsequently went on to earn a single cap for the Spain national side.
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