Shakhtar Donetsk president Rinat Akhmetov has told Chelsea the price they need to meet for Willian.
Willian is the latest player to be linked with a move to Stamford Bridge as the European champions continue to look to rebuild their squad this summer.
"I am sure that Willian will remain in Donetsk," Akhmetov told Shakhtar's official website.
"As for big clubs' interest in our players, we don't have a golden cage here - we are open to talks. And when an offer suits Shakhtar, we let a player leave.
"Regarding this situation, I clearly said that I would not even talk about a sum that is less than €30million.
"And if Chelsea or any other club offers for him the aforementioned sum I will let him go. At present, we have no such proposal.
"I am not waiting for an offer of €30million and do not want to be offered this amount of money which will result in us having a headache. Willian is a very important player who can help us."
Akhmetov recently met with Chelsea owner Roman Abramovich.
"He also said that he is a very good player.
"But, as I understand it, they are not going to pay this kind of money. And I know that we're not going to sell Willian for a lesser sum.
"I would not want us to receive such an offer. But if we receive it, I will respect the player's ambitions. If we don't receive it, Willian will remain at Shakhtar."