French-born Argentina international Higuain, who joined the Spanish club in 2007, has enjoyed a successful season at the Bernabeu, helping them to the runners-up spot in the Primera Liga and proving himself as a prolific goalscorer.
But Maradona has revealed the 22-year-old forward confided in him that Los Blancos have not approached him about a renewal of his current deal.
"When I saw Higuain I asked him if he had renewed his contract for 10 years and he replied that nobody had got in touch with him yet," said Maradona.
"I said to him to be calm and to let his father (Higuain's agent) get as much money as possible from the club. If not, they will sell him for €70 million (£60.9m)."