Bayern Munich chief Matthais Sammer insists Mario Mandzukic is not for sale.
The Croatia striker is a top target for Chelsea, Liverpool and Arsenal this summer.
But, speaking to Sky Deutschland, Sammer warned: "No one needs to start knocking on our door about Mandzukic.
"He is incredibly important to Bayern.
"I always affectionately say that he plays like an animal. It is simply amazing how much work he does for the team and how much running he does during a game.
"They always try to provoke him because he really hurts his opponents with his work-rate."
