American 21-year-old Brandun Lee, one of boxing's most devastating punchers, returns to the ring Saturday

• Brandun Lee is one of boxing's big punchers in the 140-pound weight class.
• The 22-year-old American has known for a decade that he can knock people down and out.

Brandun Lee was just 12 years old when he dropped somebody with a punch for the first time.

"From a young age I started noticing I had power," the American boxer, now 22, told Insider this week ahead of his 24th pro fight. He takes on Juan Heraldez Saturday at the Dignity Health Sports Park in Carson, California.

Lee, who is as yet undefeated, is from nearby La Quinta, and is developing a fearsome reputation as a puncher. He's won 21 of his 23 pro boxing bouts to date by knockout.

He's been a knockout artist for almost a decade, he told us. That first knock down at 12 developed into pure knockouts by 14.

At 15, he was knocking even more people out.

When he first realized he had dynamite in his mitts, he switched styles. He was previously a point-based boxer in the amateur system, looking to throw a lot of punches to win each round in a three-round bout.

But as a teenager, he got more aggressive, switching to a pro style, he said.

Still young for a fighter, it is already paying off for Lee as early this year he scored a thunderous finish that roused the ShoBox commentary team.

The booming right hand in the third round separated Samuel Teah's senses before he'd even hit the deck.

For Lee, it was a knockout shot he'd sensed was coming. "I knew he wasn't 100% there and when I connected with another clean shot, I knew he wasn't going to get up," said Lee. "Especially because of the way he fell."

The aftermath was "incredible," he added, as he disappeared backstage and felt like he was "on the Moon."

He said: "I was so happy as I worked so hard for that and it was my biggest test. I felt like I was maybe overconfident, though, because I was in the locker room and one of the reporters asked me, 'What did you learn from this fight?' And I said, 'I didn't learn anything.'

"But that was just the ego speaking because in every fight you learn something, and in that fight I learned that I got caught with a couple jabs, and you have to keep you right hand up, and use head movement.

"So when I said that, I was just being foolish."

Are punchers born or made?

Lee has been a heavy hitter for half of his life, and says it's a skill you're born with, rather than one you can just develop.

"You can't generate power and you can't build power," Lee claimed. "You're either born with it, or you're not. And so I'm blessed to have this speed and power — that's what people keep telling me."

Such is Lee's power-punching reputation at home, that friends of his, and strangers who know of him, issue bizarre challenges.

"Once in a while I get buddies of mine who say, I want to do the body-shot test with you. And I'm like, 'Come on, man.'

"I even have random people coming up to me, saying: 'Brandun Lee, can you hit my arm or hit my face?'"

He declines the challenge, but mainly because he doesn't want to needlessly risk injuring his hands.

Lee fights Juan Heraldez on a PBC on Showtime card this weekend

Lee's opponent Saturday, which kicks off the Premier Boxing Champions on Showtime event, is a Mayweather Promotions fighter called Heraldez.

This, Lee claims, is an indication that he cannot underestimate who he is sharing the ring with. "Mayweather Promotions don't sign just anybody," he said.

Lee added: "He's fought Regis Prograis. I've watched a lot of film on him and he's a boxer with decent head movement and nice speed."

To counter what Heraldez may try once the opening bell rings, Lee said he's been training "everything."

"Specifically, we're working with two styles — the puncher's style, and the boxer's style. So I was sparring one guy, 5-foot-8, a straight puncher who just comes forward.

"And I had two other sparring partners, one guy was 6-foot-3, 17 years old, 160-pounds — a boxer. And another sparring partner was a 140-pounder and an Olympic silver medalist who can turn leftie and rightie.

"I'm 110% prepared for whatever he brings to the table," he said.

"I'm expecting the dog to come forward and the sheep to go backward," Lee added, referencing himself as the dog in this instance.

"He won't fight me one-on-one and man-on-man. He'll try and run circles around me, try and catch me off guard. But whatever he brings to the table, we're 100% prepared for it. And Saturday night — it'll be 24-0.

"I know I'm stronger than him, I hit harder than him, and more experienced than him. I'm sparring better opposition than him. So even if I do knock him out, it has to be about the way I knock him out.

"I'm looking to be a world champion in 2022, and a unified champion, and then look up at 147."