With the ominous strains of Enter Sandman now fading away into the lively beat of mariachi music, "Brocktober" has ended on a disastrous note for former UFC heavyweight champ Brock Lesnar.

Following his one-sided loss to Cain Velasquez at UFC 121, Lesnar will face a stiff challenge as he attempts to fight his way back to the top of a division he dominated so thoroughly only a year ago. But if one thing is certain, it is that Lesnar is a born competitor, and fans can look forward to seeing him come back with a vengeance the next time he steps into the Octagon.

The question is, who will he face?

Although the heavyweight division in the UFC is arguably more full of talent at the top than it ever has been before, most of the big names are already committed to upcoming fights. Velasquez looks set to defend his belt against top contender Junior Dos Santos, while Shane Carwin, the last title challenger, will be squaring off with Roy Nelson next time he enters the cage.

That being said, there's still plenty of talent left in the division. Here are five intriguing matchups for Lesnar when he makes his return.

Antonio Rodrigo Nogueira. With some of the most exciting battles in MMA history on his resume, including victories over almost all the big names in the division, the former Pride heavyweight champ is a legend in the sport. Although "Minotauro" has struggled at times in the UFC he is still a man who commands tremendous respect, and a fight with Lesnar would be a surefire sell for the UFC.  Nogueira, like Lesnar, is coming off a defeat to Velasquez, which could also make for a compelling storyline to any fight between them.

Frank Mir. With the series between them tied at 1-1, a third fight to settle the score once and for all is a distinct possibility. Mir, who has demonstrated a sort of obsession with fighting Lesnar again, would be sure to jump at the opportunity. It's hard to imagine that Lesnar would turn down the opportunity to once again face the man who submitted him in his first UFC fight either. Hyping the fight for the fans might be a bit harder sell, but if the past is anything to go by, it wouldn't take long for the sparks to fly between these two and the excitement to follow.

The loser of Carwin vs. Nelson. With Shane Carwin and Roy Nelson set to meet at UFC 125 following losses in their last fights, the loser is going to face a tough test to get back to the top ranks of the division. Lesnar would provide just such a test. Carwin gave Lesnar an extremely tough fight when the two men met at UFC 116 earlier this year, and a rematch between them would be sure to be thrilling. Nelson possesses supreme self-confidence and has already mentioned Lesnar's name several times as a prospective opponent. The UFC seems more than happy to give "Big Country" his wish of big opponents, and he just might get to face Lesnar even sooner than he imagined.

Cheick Kongo. The French kickboxer with a penchant for grabbing his opponent's shorts and a seeming inability to develop a ground game would be a big step down for Lesnar, but he would offer the UFC a chance to ease the former champ back into the win column against an opponent with big name recognition and an imposing physical appearance. For...