An Everton spokesman said: "The manager needs his best players at the moment, and Thomas is certainly one.
"Our battle is to stay in the Premiership, so if anyone makes a small bid for a player thinking he is going to be cheap in the final year of his contract, they are very much mistaken.
"We need our best players on the pitch to protect our position in the top flight, he is more valuable to us here that letting him leave for a million or so."