I don't think he's afraid or apprehensive regarding Lesnar. He's faced and dominated elite and more experienced opponents before. He's truly put it on the line every time he's fought and he doesn't fight to eke out wins. Plus, he's from Stary Oksol. Fear has never been part of his makeup. I also don't think he cares about his perceived legacy as much as Fedorites do.
That's not to say that Lesnar can't beat him. Anyone that big, strong and agile is capable of beating anyone else.