There could be worse feelings to have while competing in the Octagon, but if there are, Charlie Brenneman doesn’t know about them.

What he does know is that in the midst of his 2011 fight with UFC 210 headliner Anthony Johnson, he got rocked by “Rumble” but made it to his feet. His legs were somewhere else, though, so he needed a couple seconds to steady himself. Johnson, who faces Daniel Cormier on Apr. 8 in Buffalo, wasn’t interested in such a plan.

"It’s like sprinting into a brick wall and saying, ‘I can’t stop’ and boom, you hit the wall.” --Charlie Brenneman on getting hit by Anthony Johnson

“When my shoulder hit the cage, I remember seeing him take that stutter step into his high left kick and seeing his foot leaving the ground and coming to my face, but not having the brain-muscle connection to do anything about it,” Brenneman recalled. “I saw it, like a baseball bat, coming right at my face. It’s terrible. It’s like sprinting into a brick wall and saying, ‘I can’t stop’ and boom, you hit the wall.”

Johnson’s kick drilled Brenneman and not only ended the fight, but landed on the victor’s eternal highlight reel. By then, the Georgia native was already one of the sport’s premier finishers, with seven of his 10 pro wins ending via knockout.

Of those seven KO victories, six came in the UFC, where Johnson was a rapidly rising welterweight star. The only man to go the distance with him up until that point was British star Dan Hardy, who was coming off a knockout loss to Carlos Condit when approached with a March 2011 fight against Rumble.

“There was a part of me that thought to myself, ‘I’ve pissed off somebody in the UFC. I don’t know what I’ve done wrong, but I’m coming off my first ever knockout loss, and they put me against a guy that’s never not knocked a welterweight out,’” Hardy laughed. “There’s a weird period after getting knocked out where you question whether you can take a shot anymore. My solution was to watch loads and loads of Wanderlei Silva fights because I saw that guy taking shots and walking through them and I knew that I could do that if I needed to.”

This #KOTW comes from the scariest KO artist in the UFC. Need we say more? #UFC210 pic.twitter.com/YT5fE2a4Vg

— UFC (@ufc) March 22, 2017

Not too many traded with Johnson, and those who did paid the price. But Hardy, two fights removed from going five rounds with 170-pound champion Georges St-Pierre, was willing to do so. Yet when “The Outlaw” did meet Johnson, the knockout artist showed off his wrestling skills to drill out a decision win. That doesn’t mean Hardy didn’t taste some of his opponent’s vaunted power.

"His hands - and certainly his leg when he kicked me - feel like it’s made out of lead." --Dan Hardy on Anthony Johnson

“With Anthony Johnson, it’s a very unusual power that he has,” Hardy said. “And it’s not even necessarily power that it feels like; it feels more like weight. His hands - and certainly his leg when he kicked me - feel like it’s made out of lead. It feels very weighty. It’s the same thing with (UFC vet) Paul Daley’s left hook when we used to spar. There was a weight to it. It’s almost like your head was a magnet and it attracted this massive chunk of metal to it.”

So even if Johnson didn’t get the knockout, he always got the respect of his opponents for his power. And it’s not just his opponents that felt it. Former UFC light heavyweight champion Rashad Evans has been Johnson’s friend and teammate for years. And over the course of those years, there have been plenty of sparring sessions. And they’re not always pleasant.

“You can tell how it’s gonna be when he comes to the gym,” Evans chuckles. “If he’s really, really quiet, he’s in a mood, so you have to keep your head on a swivel because he’s coming hard.”

Even against his buddy?

“He tries not to go hard, but then it takes one hard punch that he feels, and then all hell breaks loose and then he opens up and he goes pretty hard,” he said. “I’ve watched him knock out countless people in the gym.”

That’s scary, but what’s scarier is that Johnson’s power is almost effortless.

“He hits ridiculously hard,” Evans said. “And the thing about it that makes his punching power so unique is that it’s effortless. He’s not trying to hit hard, he’s just swinging and that’s the crazy thing about it. Sometimes we’re just going light and he’ll throw a punch and I’ll go, ‘Yo, we’re going light.’ And he’ll say, ‘I wasn’t trying to hit hard, I was just swinging.’ And he really was. But he’s got these heavy, dense bones. And when he hits you, it’s not a pain. Usually it’s like a thud, and maybe your lights will flash for a little bit. He caught me with a couple of those and I’m like, ‘Woo, we’re sparring right now, huh?’”

"And when he hits you, it’s not a pain. Usually it’s like a thud, and maybe your lights will flash for a little bit ... He’s the hardest puncher I’ve ever experienced, for sure. No doubt about it." --Former champion Rashad Evans on Anthony Johnson

So where would Evans, who has tasted heat from the likes of Chuck Liddell, “Rampage” Jackson, Thiago Silva, Dan Henderson and Glover Teixeira, place Rumble?

“He’s the hardest puncher I’ve ever experienced, for sure. No doubt about it.”

Impressive. Yet what may be more notable is that when weight issues forced Johnson to leave the welterweight division and test the heavyweight class before settling in at 205 pounds, he carried his power with him, as his last five wins have been knockouts of Rogerio Nogueira, Alexander Gustafsson, Jimi Manuwa, Ryan Bader and Glover Teixeira.

After the Gustafsson fight, which Johnson ended in a little over two minutes, Hardy - who does color commentary for several of the UFC’s European shows - ran into his former foe.

“I saw him in the hotel and I said jokingly, ‘I’m glad you didn’t do that to me. And he grabbed me by the shoulder and said, ‘That’s because I like you, man.’”

And that’s the thing. As ferocious as Johnson is in the Octagon, he’s humble and laid-back outside of it. There are no trash talk wars, no bad feelings with his opponents. But when it’s time to go, he’s looking to take an opponent’s head off, and they know it. Brenneman, who was coming off a career best win over Rick Story when approached with the Johnson fight, certainly did.

“Immediately after I beat Story, I sat down with my team and we objectively looked at everything and said, ‘Who’s the best matchup, who’s the worst matchup?’ And Johnson, we objectively deemed, was the worst matchup. (Laughs) That being said, I was excited for it. I wasn’t nervous, I looked at it as another fight and in my mind, I thought I’m gonna win this fight because I’m gonna outwrestle him, push the pressure and tire him out.”

The two did go to the mat early in the fight, but Brenneman got a painful jolt that let him know it was going to be a rough night.

“I was underneath him and I remember for the first time in my fighting life, thinking, ‘Ouch,’” he said. “He was coming from a weird angle, but punching me. And I just remember feeling the impact and thinking, ‘This is not a normal fight with a normal guy.’ And I felt it immediately. I was saying, ‘Ouch’ in my head, and anyone who fights knows that you don’t usually think that or feel that. It’s more like just a thud, thud, thud. But when I was underneath, I thought this is a different one.”

How different? Hardy thinks he may be from out of this world.

“Out of everybody I’ve ever worked with, trained with, sparred, held pads for, nobody hits like Anthony Johnson, they really don’t,” he said. “I don’t like to throw around the word supernatural, but it doesn’t feel like a natural power. It feels like he could quite easily have an X-Men costume on, let’s put it that way.”