The German described his opponent as the world's "number one heavyweight" and expressed his respect for him.
"Vitali Klitschko says every time that he wants David Haye, but he is afraid of David Haye, who, for me, is the number one heavyweight," Charr told reporters.
"I respect him. He is a great fighter."
Haye, who lost his WBA belt to Wladimir Klitscho in July 2011, is targeting a title shot against one of the Ukrainian brothers by working his way up to a mandatory challenger position.