Brock Lesnar could absorb the beatings he suffered inside the cage.

Lesnar was built to fight — to conquer all — on a mat, in a ring or inside metal, and no man could cross over genres and collect championships with his ease. His rapid ascension from faux fighter for WWE to heavyweight champion under the UFC banner made the superhuman freak the pay-per-view box office king, one of the baddest men in sports and put him on a seemingly lengthy career path toward MMA immortality.

But the determination and domination that allowed him to knock out Frank Mir and Randy Couture and choke out Shane Carwin couldn’t help Lesnar defeat diverticulitis. The lower-intestinal ailment nearly killed him, and it forced him to retreat back to WWE in 2012.

“It haunted me for a long time,” Lesnar.

Turns out, Lesnar wasn’t finished with UFC.

Fire up the Brocktagon one more time.

One year after he closed the door forever on a UFC return, Lesnar is set for the surprise comeback of the year, fighting Saturday for the first time in 4 1/2 years, against heavyweight Mark Hunt in the co-main event of UFC 200 in Las Vegas.

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“I truly, 100 percent thought he was done and we’d seen the last of him in professional fighting,” UFC President Dana White told The Associated Press. “The WWE, that deal was the right move. It was the right money. At that point in his life, I thought it was perfect. What he accomplished here was incredible but it was probably time to move on.”

Going out on an Alistair Overeem kick to the liver would have been one thing. But Lesnar, who turns 39 three days after UFC 200, could not accept that 12 inches of surgically removed colon would be his final parting blow in UFC.

Lesnar won the NCAA heavyweight championship at Minnesota and wrestled WWE greats Hulk Hogan, The Undertaker and The Rock in PPV main events in his early 20s. He’s always been a competitor, and that edge had him calling White late this spring asking for another fight.

“Before it’s too late, I want to get back in the cage and have some fun with it,” Lesnar said. “This is all about having fun. I’m not looking past this fight.”

Lesnar was a man resigned to MMA retirement last March when he went on ESPN and announced he had signed a contract extension with WWE. He told the AP he turned down a UFC offer worth “10 times” what he was making earlier in his MMA career.

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“I’m a 37-year-old man, and some days I feel like I’m 80, just with all the things I’ve experienced, all the things I’ve done. I feel fortunate about it. It’s like, what else can I do? Why go backward?” he said last year.

Lesnar needed approval from WWE Chairman Vince McMahon to return to UFC. After a few phone calls of negotiations with White, a deal was struck that allowed Lesnar back in the octagon.

WWE refused to make any officials available to the AP for comment. WWE chief brand officer Stephanie McMahon told Business Insider last month the company is, “not supporting the fight, necessarily” but agreed to let Lesnar fight for UFC because he was a special attraction.

“We recognize the value of our performers participating in entertainment and sporting events outside of WWE,” the company said in a statement.

Win or lose Saturday, Lesnar is scheduled to have his next WWE match Aug. 21 at SummerSlam in New York.

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For UFC 200, Lesnar told White to put him in the cage against any fighter. Lesnar said there was early talk his return would wait for the inaugural UFC New York card in November, but White had a vacant spot on this weekend’s card when it pushed the McGregor-Nate Diaz bout to UFC 202.

Lesnar (5-3) fights the 42-year-old knockout artist Hunt (12-10-1) on a card now headlined by women’s bantamweight champion Miesha Tate vs. Amanda Nunes. (Daniel Cormier vs. Jon Jones was the original headliner until Wednesday night when it was announced Jones had tested positive for a banned substance. Cormier now will fight Anderson Silva). Hunt has nine fights since Lesnar’s last bout in December 2011 and knocked out Mir in March at UFC Fight Night in Australia.

“Is he better than I am at standup? Of course he is,” Lesnar said. “Is he a better wrestler than me? Hell no.”

Happy with his family in Saskatchewan and healthy for the first time in years, Lesnar is enjoying his training camp like never before. White said he has never seen Lesnar “so excited and almost giddy” as he has been the past month, and so even though Saturday’s bout is “absolutely a one-fight deal,” there’s no guarantee that it’s the last UFC sees of Lesnar.

“Nothing is ever final,” White said. “This is a one-and-done, but who knows? He could come back again.”