MELBOURNE, AUSTRALIA - NOVEMBER 15:  Holly Holm of the United States knocks down Ronda Rousey of the United States in the second round in their UFC women's bantamweight championship bout during the UFC 193 event at Etihad Stadium on November 15, 2015 in Melbourne, Australia.  (Photo by Scott Barbour /Zuffa LLC/Zuffa LLC via Getty Images)