Goretzka has just one year left to run on his current terms at the Veltins-Arena, but Schalke are determined to keep hold of their star man no matter how much money is tabled for his signature.
"We'll definitely go into the next season with Leon," FourFourTwo quotes Heidel as saying. "Maybe he is the most important player for us. It makes no sense to us to let him leave ahead of this season.
"It does not have to be a European club, a Chinese one can come in. That does not matter to us."
Goretzka is a part of Germany's Confederations Cup squad, scoring three times in three appearances to help his side to the final.