Husillos admits that they would be powerless to prevent the 20-year-old from leaving in January should someone agree to pay the youngster’s €21 million buyout clause.
Isco has been linked with the likes of Tottenham, Arsenal and Manchester United.
“He is our player and is important for the team. He is not on the market,” Husillos told tuttomercatoweb.com.
“We want to keep him here but you all know there is a buyout clause in his contract. So, if a club pays the clause, it does not depend on us anymore.”