Velasquez (12-1) is the UFC heavyweight champion, but Dos Santos (16-2) has taken that title from him once before. That happened in their first meeting, the debut of "UFC on FOX" on Nov. 12, 2011 at Anaheim, Calif. Dos Santos knocked out Velasquez in the first round for the championship.
Velasquez regained the title at UFC 155 on Dec. 29, 2012 at Las Vegas. He prevailed against Dos Santos by unanimous decision in a fight that was not close. Velasquez has defended the title once since, defeating Antonio Silva by TKO at UFC 160.
Dos Santos' only fight since his loss to Velasquez also came at UFC 160. He knocked out Mark Hunt with a spinning heel kick and punch in the third round to earn another crack at Velasquez.
The October event, expected to be staged as UFC 166, will be held in the Toyota Center. That venue has hosted UFC cards twice before, in 2007 and 2011.