Mir has also never found himself in this situation: If he wins, it's no big deal, and if he loses, he could be letting down the entire MMA universe.
Without question, the Brazilian jiu-jitsu practitioner is marred in a precarious position whether he wants to admit it or not.
Mir is fighting Lesnar in the featured attraction of Saturday's UFC 81 card inside the Mandalay Bay Events Center, though his duel with the former NCAA wrestling champion turned professional wrestler is not the bill's main event. The Mir-Lesnar matchup has mutated from potential circus act into one of the more ballyhooed showdowns in recent memory.
Even snobbish cynics have had their interests piqued for the heavyweight encounter and for good reason. It's the perfect clash between a well-rounded, seasoned professional fighter and a popular genetic monstrosity who etched his name by capturing gold in scripted battles.
However, the bout is not some sort of wacky carnival act of real fighter versus cheesy pro wrestler, as some have suggested. As Mir himself will attest, Lesnar is not someone to be taken lightly; he is a genuine and formidable opponent, a champion of real wrestling as much as the phony kind.
"I know he's got a great collegiate wrestling background," Mir said recently. "He's very limited, but he's determined in what he knows and that is takedowns and ground-and-pound. … So with that, he certainly has legitimate roots of being an MMA fighter. Even if he never had a career in pro wrestling, he would have been an MMA fighter."
Aside from Lesnar's collegiate pedigree and underrated athleticism, it's no secret that he possesses enormous strength. Mir has remarked that it would be unwise to just stand in the Octagon and let Lesnar plug away with his power.
"Don't be stationary," Mir warned himself. "Obviously Brock is a lot stronger than I am; it doesn't take a genius to figure that out. He's stronger than probably most everybody he can compete against. So if I just lay there, I'm going to get crushed. I have to use speed, motion and movement."
Speed and movement is something Mir will presumably have to his advantage, but the brutish power of Lesnar could offset both. Then there's Mir's undeniable submission prowess, which could be the Achilles heel of the brawny Lesnar, who isn't quite as accustomed to armbars and leglocks as he is to steel chairs being bashed against his cranium.
"Well, he's been training in MMA for a few years now, and I'm willing to bet that he's been [working on] plenty of submissions," Mir said. "Technique usually beats sheer size and strength, and I'm confident that my jiu-jitsu will give him problems. He's never had to escape real chokes or armbars in [pro wrestling]. But if that doesn't work, there are other avenues I can explore. This is a fight, after all."
The other avenue Mir hinted at is one not many delve into when discussing this fight: striking.
Granted, Mir isn't a carbon copy of Anderson Silva or Mirko Filipovic (Pictures), but he can hold his own and has decent knockout power. He questioned whether Lesnar has been truly hit before, considering the two forms of wrestling he excelled in didn't allow actual strikes.
"Obviously every fight starts on its feet, and I am going to utilize as many different techniques as possible," Mir said. "But yeah, when I close the distance, I am going to strike as much as possible."
A win, especially some sort of lightning-quick submission, is something hardcore MMA fans are praying for. For reasons known only to those individuals, this fight has taken on somewhat of an "us against them" theme, with Mir representing the truest form of real fighting while Lesnar is the personified figure of fallacy.
"I don't look at it that way," Mir scoffed. "He's a huge, strong guy, and like I said he's got a great wrestling background. … He does have good credentials being that he's an NCAA champion in wrestling. Also just the sheer size of the guy and the way he looks. The average fan is going to assume some kind of success by beating him just because of his physical attributes. And besides, most people who will watch our fight will realize that he's a real fighter and not just some ex-pro wrestler."
In preparation for Lesnar, Mir said he brought in dozens of massive wrestlers. He realizes that he must be in the best shape of his life -- mentally and physically -- to topple someone like Lesnar, especially when a win could place him within striking distance of the UFC heavyweight title.
"I think [a win] would because as Brock knows by being a pro wrestler, it's not only about being a good fighter but also about being a draw," Mir said. "So I feel that with all the publicity that Brock Lesnar (Pictures) can bring to a bout between the two of us, if I can come away victorious, then yeah. But it also depends on what happens in the bout between Tim Sylvia (Pictures) and Antonio Nogueira. If Sylvia wins, obviously it puts me up a bit higher because of our history, but if Nogueira wins, then it puts me up there with whoever else is already up there."
By "up there," Mir means near the top, where he was before a horrendous motorcycle accident in 2004. His career since then has been a struggle, but he still has the tools necessary to be the heavyweight champion.
In fact, some believe he's already on the road back -- a path that on Saturday must go through Brock Lesnar (Pictures).