Brock Lesnar isn't your average professional wrestler. While some WWE performers have a background in amateur wrestling, football or mixed martial arts, Lesnar has competed in all three. And amazingly, the latter two actually came with no prior experience after he had already established himself as a pro wrestling superstar.

His in-ring persona is that of a "beast incarnate," as manager Paul Heyman describes him. But Lesnar isn't some over-the-top character who needs a hype man. His achievements outside of pro wrestling have added some legitimacy to a company that hasn't really sought it since 1989, when WWE honcho Vince McMahon admitted pro wrestling was, well, more entertainment than sport in order to avoid the watchful eye and hefty fees of state athletic commissions.

We're not quite sure how Hulk Hogan or Ric Flair would have fared in a freestyle wrestling match, an NFL game or a UFC fight, but we've seen Lesnar in all three -- and we've also watched him suplex both Hogan and Flair for good measure. Lesnar is the most accomplished athlete in pro wrestling history and a big reason why the WWE is getting more mainstream attention than it has in years. His decision to turn down an opportunity to return to the UFC and re-sign with the WWE earlier this year got widespread media coverage and was announced on SportsCenter.

Brock Lesnar celebrates with Paul Heyman after pinning The Undertaker at WrestleMania XXX. AP Photo/Jonathan Bachman

Before Lesnar headlines WWE's annual SummerSlam pay-per-view event Sunday at Barclays Center in Brooklyn, let's take a look back at some of Lesnar's greatest accomplishments in and out of the ring.

NCAA heavyweight wrestling champion

Lesnar's athletic career began in Webster, South Dakota, where he went 33-0 as a wrestler during his senior year at Webster High before winning the national junior college championship at Bismark State College. Lesnar then transferred to Minnesota on a full wrestling scholarship and established himself as a two-time All-American.

He won the Big Ten title and finished second in the NCAAs as a junior at Minnesota before winning the Big Ten again and claiming the 2000 Division I national heavyweight championship as a senior. He finished his college career with a 106-5 record, and his "Wheel of Death" maneuver in the 2000 NCAA tournament is still talked about to this day.

Youngest WWE heavyweight champion

Lesnar's next stop was the WWE. At the age of 25, he became the youngest heavyweight champion in the history of the company. His journey from rookie to champion was also the second fastest in WWE history, claiming the belt just 126 days after making his debut by defeating Dwayne "The Rock" Johnson at SummerSlam in 2002. Lesnar would be one of the company's biggest stars before deciding to step away from wrestling in 2004 following WrestleMania XX to test himself in the NFL.

Lesnar goes to camp with the Vikings

Lesnar saw preseason action with the Vikings and was offered an NFL Europa spot, which he passed up. AP Photo/Jim Mone

Lesnar never actually played a down in a regular-season NFL game, but the fact that the Minnesota Vikings signed him to a rookie contract and he made it through an entire training camp before being cut is impressive for someone who never played college football. In fact, when the Vikings signed him in 2004, Lesnar hadn't played football since 1996, when he was a defensive lineman in high school. Glen Mason, Minnesota's football coach when Lesnar was wrestling at the school, tried unsuccessfully to get him to join the team on several occasions.

In Lesnar's first NFL preseason game, he recorded a tackle and forced fumble. Lesnar later said he felt unprepared for the challenge of trying to make an NFL roster as a 27-year-old rookie who hadn't played a down of football in nearly a decade. The Vikings saw enough raw talent and potential to offer him a spot on an NFL Europa team, but he passed and retired from football.

UFC heavyweight champion

When Lesnar signed with the UFC in 2007, he had only one mixed martial arts fight under his belt -- a first-round win earlier that year over Kim Min-soo, a kickboxer with a 2-5 MMA record. Lesnar lost his first UFC fight to Frank Mir, submitting to a kneebar, before returning six months later to win a unanimous decision over Heath Herring.

Despite having just a 1-1 record in the UFC, Lesnar was given a title shot against heavyweight champion Randy Couture in 2008. He made the most of his opportunity, defeating Couture in the second round with series of hammer fists that forced the referee to step in. In 2009, Lesnar avenged his loss to Mir by stopping him in the second round with another flurry of fists.

In their second meeting, Lesnar pounded out a win over Frank Mir to avenge a loss in Lesnar's UFC debut. Martin McNeil for ESPN

After an intestinal illness required surgery and prevented him from fighting for a year, Lesnar successfully unified the UFC heavyweight championship by submitting Shane Carwin, who had won the interim championship while Lesnar was out. Lesnar looked like a shell of his former self, however, in losing his title to Cain Velasquez via strikes in the first round in 2010. He fell ill again and needed more abdominal surgery before suffering another first-round TKO at the hands of Alistair Overeem on Dec. 30, 2011. Lesnar retired from the UFC after the loss.

Lesnar breaks Undertaker's streak

Lesnar returned to professional wrestling in 2012. It didn't take him long to reclaim his spot atop the company, winning the WWE heavyweight title for a fourth time. But the signature moment of his wrestling career came with no title on the line last year. Lesnar broke The Undertaker's 21-0 WrestleMania record, pinning him in front of a stunned crowd at the Superdome in New Orleans. On Sunday, Lesnar will once again take on The Undertaker as he tries to add to an already impressive list of accomplishments.