It was revealed earlier this week that Spurs had failed with a €10 million bid for Hernandez.
When asked about Tottenham's offer, Hernandez's agent, Vincenzo D'Ippolito, told calciomercato.it: "It's true.
"But for the time being I know (Palermo president Maurizio) Zamparini has turned down the offer, although I do not know what the figure was.
"If indeed it was 10 million then it would be considered too low as the value of the player in the market is 20 million.
"The transfer market has just started so we will see what happens."