In this Dec. 2, 2017, file photo, Francis Ngannou, left, hits Alistair Overeem in the first round during a UFC 218 heavyweight mixed martial arts bout, in Detroit. Ngannou defeated Overeem by first-round knockout. Ngannou has knockout power that snaps heads back like Pez dispensers and earned him comparisons to Mike Tyson in his ferocious heyday. Ngannou will compete in the heavyweight champion bout against Stipe Miocic in the main event of UFC 220. (AP Photo/Jose Juarez, File)