Last time they stepped into the cage, it took Junior dos Santos just 64 seconds to irrevocably change not just the heavyweight landscape, but our entire perception of deposed champion Cain Velasquez.
Before that telling moment when a thudding right hand to the temple sent him reeling, Velasquez was an unstoppable monster, a man so daunting that manager and trainer Bob Cook had a hard time finding anyone in the sport's minor leagues to test him.
Two years passed by with just two fights booked. Cook looked everywhere, but Velasquez's reputation and wrestling pedigree were too much for most prospective opponents. Eventually Cain, with minimal experience, was forced to learn his trade in the UFC's Octagon.
It was a dangerous proving ground, but the wrestler found his way, winning six consecutive fights before taking the title from Brock Lesnar. In his five-year career he was rarely tested and never beaten. His combination of volume striking and superb wrestling was to be the template for all heavyweights to follow.
Dos Santos changed all of that. Suddenly, even moments that had previously been feathers in Velasquez's cap became telling signs of weakness. The media and fans had helped build Cain Velasquez into a mythical creature. Instead, he turned out to be merely a man. In our modern era, that couldn't stand. The virtual Velasquez statue had to come falling down. And plummet it did.
His toughness and ability to walk through even the strongest punches en route to eventual victory?
Now seen as signs of a weak chin.
His willingness to mix it up standing?
What was a virtue, a sign he was a complete fighter, suddenly looked to many (including UFC president Dana White) like a stubborn refusal to utilize his wrestling strengths.
The critiques just kept coming. Even after video surfaced showing Velasquez had entered the fight with a serious ACL injury, all many could see were his flaws.To his great credit, Velasquez refused to make the knee injury an excuse for his loss.
"Just me being a fighter," Velasquez said in a media conference call 10 days before the second fight. "Junior was hurt as well. Guys get injured before the fight so it was just me being a fighter and not backing out. I did it, and it's in the past."
Why would a champion take on a challenge like Junior dos Santos at less than 100 percent? Velasquez credits, or faults, depending on your perspective, the mentality that drove him to the top. Through it all, he simply put his head down and went to work.
His return at UFC 146 left prospective contender Antonio Silva laying, not just on the mat, but in a pool of his own blood.
"It was a mauling by the former champion," announcer Joe Rogan said. "He did everything perfect. There were no flaws in his performance, no flaws in his game plan."
In a short-staffed heavyweight division, weakened by the retirement of Lesnar and suspension of Alistair Overeem, that was enough to earn a rematch with the new kingpin.
What will be different this time? Don't count on Velasquez, a man of few words, to tell you.
"I just want to go out there and fight my fight," he said. "That's it."
Velasquez's fight, for the uninitiated, is wrestling-based. A former All-American at Arizona State, Cain is one of the best top control grapplers in the sport, finishing most of his fights with devastating ground-and-pound. It was an aspect of his game missing from the first bout, one in which he seemed content to try to counter dos Santos standing.
In the first fight, fans didn't get to see any action that will likely tell the tale this time. The fight hinges, in many ways, on Velasquez's ability to take the bout to the ground and keep it there against the champion. In the first bout, things never progressed to the clinch, with dos Santos making the point moot with his spectacular knockout. It's unlikely to play out quite so cleanly again.
Dos Santos is most effective standing unusually upright, reminiscent of boxing's Klitschko brothers, employing his deceptive speed to leap into and back out of range. Employing a jab and a straight right to the body, dos Santos hopes to bait opponents into chasing him as he retreats, countering their bull rush with a sneaky left hook.
In many ways, Velasquez is an opponent tailor-made for the champion. He is aggressive, almost to a fault, charging forward recklessly at all times in an effort to finish the fight. Against dos Santos, this is a death sentence. To win, Cain will need to adjust fire.
Who do you have?
The best counter to a typical boxing stance is the leg kick, as Rory MacDonald showed against B.J. Penn and Ben Henderson demonstrated against Nate Diaz. Velasquez has a hard kick, but has also routinely been tagged trying this technique against even average strikers. I'm not sure it's the answer for Cain against the champion.
Against dos Santos, as it has so often in MMA history, the bout boils down to whether or not Velasquez can bring the striker to the ground. No, it's not as simple as "grappler versus striker." But in a way it absolutely is. Dos Santos, for his part, agrees.
"For sure, I think Cain Velasquez is gonna come hungrier for this fight, to try to work his game, try to take me down and use his ground-and-pound, which he uses very well," the champion said. "My strategy is the same strategy, and I'm prepared for this fight and ready to win."
Both fighters claim to be 100 percent this time. Will good health alone be enough for Velasquez to reclaim his status as the baddest man on the planet? Or does dos Santos simply have his number? That no one can convincingly answer either question is what makes this one of the most compelling main events of the entire year.