The 20-year-old midfielder only signed a four-year extension in July but continues to court interest, with Chelsea and Manchester City reportedly preparing summer bids.
When asked if the youngster had a release clause in his existing deal, Martinez told The Daily Mail: "No, there are no buy-out clauses in any of the contracts. The only one was with Marouane [Fellaini] and that wasn't triggered, so it didn't matter."
The Toffees manager went on to claim that he was happy with the speculation linking the youngster with a move away because it is indicative of his form.
He added: "All the speculation and talk is positive. Because you don't get any of that when your players are not playing well or they haven't got potential."
The England international is contracted to the Goodison Park club until 2018.