Valencia determined to hold on to Mata
Mata, a member of Spain's World Cup winning squad last summer, is said to be a target of several Premier League sides, including Arsenal, Liverpool and Tottenham Hotspur.
But the Mestalla side are determined to retain the 23-year-old's services, having previously been forced to sell the likes of David Villa and David Silva.
"Juan Mata is not for sale," Valencia president Manuel Llorente told Superdeporte.
"We have no plans to sell and we have not received any formal offers for the player.
"The news that has appeared in the papers is nothing more than speculation.
"Our plan this summer is to make our squad better and our priority at the moment is to sign a central defender."
Mata has played 172 matches for Valencia since arriving from Real Madrid in 2007, scoring 46 goals.