Not long after that, the big man was sitting on the canvas, watching Cain Velasquez celebrate as the new champion while a cageside doctor attended to Lesnar's bloody face.
Funny how quickly reality can shift in this business, often right out from under your feet.
For the moments in Saturday night's main event where he was charging forward, Lesnar looked every bit as ferocious as advertised. But when it failed to stop Velasquez from offering up any offense of his own, that's when we were reminded that we really don't know all that much about this guy who, just minutes earlier, was calling himself the best.
Consider that, in his three-year MMA career, Lesnar is a modest 5-2. The first of those five came against Min Soo Kim (3-7) and the most recent came against Shane Carwin (12-1), who put a severe beating on Lesnar before running out of gas and succumbing to a submission back in July.
Other than that, Lesnar's best victories came against an aging light heavyweight in Randy Couture and an up-and-down former champ in Frank Mir.
Not to belittle what Lesnar has accomplished after coming to MMA relatively late in life, but it's hard not to feel like, either due to his physique or his background, Lesnar's hype got a little ahead of his skills.
Maybe we confused physical potential for actual ability and accomplishment. Maybe, as all things tend to do in the age of the internet, his career life cycle got too accelerated in the eyes of fans and the media. Or maybe he just took his opponent a little too lightly and got the beatdown that usually comes with that mistake.
Lesnar's plan against Velasquez seemed to be to bully him with size and power right out of the gates. If that plan sounds familiar, it's because that's more or less what Lesnar has tried to do to everyone he's fought. When you're an almost shockingly agile 270-pounder with college wrestling credentials, that's usually a pretty good strategy.
At least, it is until you run into someone with superior technique and enough ring savvy not to wilt under early pressure. Then charging across the cage without any set-up or strategy is a move that tells us you either think too much of your own ability or too little of your opponent's.
There's no question that Lesnar has uncommon physical tools. Without them, he likely never would have won a UFC title in his fourth pro fight, nor defended it successfully two times after that. But after watching him crash and burn against Velasquez we have to ask ourselves, what else does he have in his toolbox when being bigger and stronger isn't enough?
Can Lesnar take people down and pound on them with those mallets he calls fists? Sure. Can he take a punch and keep his wits about him? Unclear.
Against Carwin he managed to survive a bad first round to take advantage of his opponent's fatigue in the second frame. But against Velasquez he panicked and became flustered almost as soon as the punches started coming back at him.
In short, he fought an awful lot like a guy with only seven pro fights to his credit. He fought like a work in progress. He also fought a little bit like a bully who isn't at all comfortable with having someone get in his face rather than the other way around.
Baddest man on the planet? Not on Saturday night. And not against any opponent skilled enough to be something other than terrified matador to Lesnar's angry bull. Not yet, anyway.