BROOKLYN CENTER, Minn. — As a pro wrestler, Brock Lesnar was known as “The Next Big Thing.” This weekend, he’ll compete in his first big fight.

The grueling preparation for Lesnar’s Ultimate Fighting Championship debut has been under way since he signed with the fast-growing mixed martial arts organization in October.

Really, though, his training program began shortly after birth, in a small South Dakota farming town.

“I started fighting when I was real young. I couldn’t go anywhere without getting into a scrap,” said Lesnar, who will take on fellow heavyweight Frank Mir in the UFC’s featured event Saturday in Las Vegas.

“If you ask anybody I ever grew up with, I could never go out and have a good time,” Lesnar said, laughing: “It was always go out and see who we could bruise our knuckles on.”

Though Lesnar is new to the techniques of jiujitsu, karate, kickboxing and other disciplines in the ultimate fighter’s repertoire, the 30-year-old former NCAA wrestling champion sure looks and sounds cut out for this increasingly popular, violent combat sport.

After a recent workout at the Minnesota Martial Arts Academy, Lesnar sat down to talk about fighting. With his shirt off, a multitude of tattoos highlighted his hulking, 6-foot-3, 265-pound physique.

“Let’s say you have a bird feeder out, and you watch these squirrels and birds: They fight over food. That’s the way it is,” Lesnar said. “We tend to forget exactly who we are and what we’re all about. Now these wars that are going on, they’re fought with guns instead of hands and clubs like it used to be. Are we a little more civilized? Eh, I don’t know. We tend to think so, but ... fighting’s been around since the first day of life.”

The UFC has been around since 1993. Back then, it served only hard-core fans and seemed far outside the mainstream of stick-and-ball sports. Sen. John McCain once famously dismissed it as “human cockfighting.”

But under the leadership of Dana White, a boxing trainer from Boston who convinced two casino baron friends to financially support a takeover in 2001, the rebranded and reorganized UFC has soared. White, now the group’s president, fell in love with the sport after taking up jiujitsu.

There are now five weight classes; a long, chilling list of no-nos like grabbing the trachea and attacks on the groin; and mandatory screening for everything from hepatitis to steroids. One fighter, Sean Sherk, was suspended for six months when he tested positive for a performance-enhancing drug after defending his lightweight title last summer.

Athletic commissions in 12 states sanctioned mixed martial arts competition in 2007 to raise the national total to 33, plus the District of Columbia. In 2006, 10 pay-per-view UFC events fetched more than $200 million in revenue, more than boxing brought for HBO.

The teenagers who in the mid-1990s mischievously rented VHS tapes of blood-spattered UFC fights from their neighborhood video store are now the young professionals shelling out $100 or more for tickets to sold-out UFC events all over the country. Last March, more than 19,000 people showed up for a UFC fight card in Columbus, Ohio, and produced an arena-record gross revenue of more than $3 million.

White personally negotiates contracts with UFC athletes. Some of them of start at $2,500 per fight. The elite can make millions, though the money, Lesnar said, isn’t what lured him.

He made a mint performing for World Wrestling Entertainment, but he said the contrived environment became stale.

“I enjoyed it, but after a while, I felt like I was a caged animal, you know?” Lesnar said. “It was like traveling in the circus. Get done with the show, and you were in the hotel room. Just like the old days. They put you on the train car, and you rode the train car to the next town, got out, did your deal, and they threw you back in the train car.”

So, in 2004, Lesnar left the WWE and decided to give the NFL a shot. Red McCombs, then the owner of the Minnesota Vikings, was a big fan of pro wrestling and urged the team to give Lesnar a look as a defensive tackle. He looked good enough in a tryout to get a contract and a roster spot for training camp, but technique proved more important than brawn, and Lesnar was cut before the regular season.

The experience was humbling for him.

Well, to an extent.

“If any one of those guys would’ve stepped on the wrestling mat with me, I would’ve had ’em pinned in 30 seconds,” Lesnar said.

After settling a lawsuit with the WWE over a noncompete clause in his contract, Lesnar eventually realized his wrestling talent could carry over to mixed martial arts. He joined an outfit in Japan and, in 2007, won his first official fight in 69 seconds.

Mir, whose career record is 10-3, won’t be nearly that easy, though Lesnar doesn’t lack confidence. He speaks with the usual bravado combat sports use to help sell themselves, but it’s also a natural boldness necessary for survival on that patented octagonal mat inside the UFC’s cage-style fence.

Lesnar, who won an NCAA wrestling title as heavyweight for the University of Minnesota in 2000, said he has picked up the martial arts techniques quickly. But he will still rely on those moves and tricks he learned as an amateur grappler.

“I think wrestling gives you such a backbone, that you know your body very well and you know how to control people,” Lesnar said.

His old college coaches — and perhaps some future ultimate fighters — will be among those watching.

“One thing people forget: It is the most rudiment and basic of all competition. It’s one man against another guy to prove who’s best,” said Gophers coach J Robinson, who plans to arrange for the team to see Lesnar’s fight on Saturday.

In part, to support an alumnus, but also to get riled up for the next day’s match at powerhouse Oklahoma State.

“We’ll get our gladiators, and go watch it,” Robinson said.