"If someone comes today and offers us an amount that would be irresponsible to turn down at the current time then we sell and either develop or bring in a replacement."
Gonzalez, who joined Stuttgart in 2018 on a five-year contract, said last month he had informed the club of his desire to leave.
Several Premier League clubs are reportedly interested in the striker.
"We obviously are aware of the speculation regarding Nicolas Gonzalez," Mislintat said. "We do see the possibility that someone will offer us enough money so that we are forced to consider a sale."
"But what is important is that Nico still has three years on his contract and no buy-out clause. That simply means that anything will have to come through us and at the end it will be our decision." (Reporting by Karolos Grohmann; Editing by Hugh Lawson)