Although fans and commentators alike have a tendency to overuse superlatives like the biggest and the best when describing upcoming fights, tonight's showdown between UFC heavyweight champ Brock Lesnar and challenger Cain Velasquez at UFC 121 promises to live up to the hype.

Lesnar be will attempting to defend his belt for the third consecutive time when he faces Velasquez, an amazing feat considering it will be just his seventh pro fight and his sixth with the UFC. 

Although many fans questioned Lesnar's quick selection for a chance to fight for UFC gold after going 1-1 when he joined the promotion, results have born out the faith UFC president Dana White has always shown in the huge Minnesotan.  The Octagon is an unforgiving proving ground, and in the past two years Lesnar has made it his personal domain, silencing a lot of doubters with four consecutive wins.

Lesnar's early days as a fighter were marked by the display of an outsized personality and verbal outbursts that seemed to hearken back to his days as a professional wrestling superstar, a quality that made it hard for him to gain acceptance among many followers of the sport. Never was this more in evidence than in his victory celebration after his first title defense, a rematch with Frank Mir at UFC 100. Lesnar's post-fight performance included flipping off the crowd, talking up Coors Light, and a promise to "get on top of" his wife, antics that alienated a lot of fans and later led him to publicly apologize. 

Since then, things have changed a lot for the champ.

Lesnar suffered a life-threatening bout with diverticulitis, an intestinal disorder, in late 2009. Although he made a remarkable recovery from his illness, it was obviously an experience that had a profound mental impact on a man who before then had always been in control of his own destiny.

"I believe the mind is a powerful thing, and everyday I was put in a position and had to view my life and the world in a different [way]," Lesnar said of his time lying helpless in a hospital bed.  "I got a different take on life."

Since Lesnar's return we have seen a man of few words, a champ who seems content to make his statements where it matters most, inside the eight-sided arena that has defined his life in the sport. Gone are the emotional outbursts that marked Lesnar in the past, although his eyes still speak volumes about the fiery determination that burns behind that ominously quiet exterior. 

Now Lesnar (5-1) will face what may well be the biggest test of his career in the form of the undefeated Velasquez (8-0).

Like Lesnar, Velasquez seems to have been destined for greatness in the sport since the beginning. With seven of his eight wins ending in knockout or TKO, the tough Mexican American fighter from California has proven to be a wrecking machine for the other big men of the division. And unlike Lesnar, who had to struggle from behind in his last fight against Shane Carwin, Velasquez has never really seemed to be in any trouble in the cage, using a well-rounded fight game to dominate every man he has faced.

Although noted for his wrestling skills and dangerous striking, Velasquez's most noteworthy attribute may be his exceptional cardio, unusual for a man of his size. It is a quality which comes in for obligatory praise from ringside commentators in much the same way as Chris Leben's ability to take a punch or Jon Jones's explosive athleticism. If his fight with Lesnar goes...

Make sure to check back with us the day of the event for free, live, round-by-round coverage of UFC 121 right here at FiveKnuckles.com! Join expert analyst Mike Williams as he takes you through the entire fight card blow-by-blow and then keep it right here for all the post-fight news and notes you can handle!