Coming out of UFC 100, Brock Lesnar was deemed "the baddest man on the planet." He was 3-1 in the UFC as Heavyweight champion and coming off his first title defense on the most successful PPV in the company's history. Shortly after, he was scheduled to face the hard-hitting and then undefeated Shane Carwin. Unfortunately, before they could fight, Brock was diagnosed with diverticulitis. He had to undergo surgery and it was more than a year later before he was able to step into the Octagon again.
Prior to his illness, former champion Frank Mir was Lesnar's biggest rival. He had given Borck his only career loss and hit him with a ton of trash talk leading up to their second meeting. Now, Mir says the disease left Lesnar unable to fulfill the potential he had back in 2009 (from NY Post):
Honestly, I think the guy got so ill, he just couldn’t do it anymore. He had to leave or his quality of life wouldn’t have been normal.
We didn’t get to see the Brock I fought. Had he not been ill, things would have been different
Lesnar returned at UFC 116 where he finally had his fight against Carwin. The champ took a vicious beating in the first round, but rallied in the second to earn his second title defense. Only a few months later, he lost his title to current champ Cain Velasquez via first round TKO. He'd only have one more fight in the UFC, where he was once again finished in the opening round. Since retiring from MMA, Lesnar has returned to the WWE where he most recently appeared at Wrestlemania 29.
In just 4 days, Mir has a big fight of his own to look forward to. At UFC On Fox 7, he'll be welcoming Strikeforce HWGP champion Daniel Cormier to the UFC. As an undefeated fighter and former Olympian, Cormier will be making his promotional debut with a lot of hype and high expectations behind him. His first test will be Mir who's a seasoned veteran of the sport and two-time former UFC champion.