UFC 121 is airing this Saturday and Brock Lesnar, the mutant, freak show of humanity, faces his toughest challenge yet in Cain Velasquez, heavyweight contender with an 8-0 win streak, being just the second person in UFC history to knock out AntÃÂ´nio Rodrigo Nogueira. Lesnar may have a weight advantage over Velasquez, likely weighing in around 265 while Velasquez will likely come in at 240. Lesnar can dominate his opponents on the ground with relative ease given his size but Velasquez has the cardio of a middleweight or even a welterweight and will likely outlast Lesnar, as well as display his Division 1 wrestling skills along with his hurricane fists. Jake Shields will be making his UFC debut against potential welterweight contender Martin Kampmann. Shields, who is on a 14 fight win streak will be squaring off against Kampmann in the co-main event. Dana White has previously stated should Shields win this fight, he's looking at giving Shields a shot at the Welterweight title currently held by fan favourite Georges St. Pierre. Fans can also expect Tito Ortiz to step into the octagon against Matt "The Hammer" Hammil, Ortiz former student on Season 3 of the "The Ultimate Fighter". A win over Hammil is needed for Ortiz, who is suffering from a bit of a dry period regarding wins. Ortiz has not won a UFC fight in 4 years.