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At 47 years old, Herschel Walker knows he's not going to have a Hall of Fame career in mixed martial arts.

He knows he'll never fight for a heavyweight title or headline a pay-per-view. So what would make a College Football Hall of Famer and former NFL star running back take a chance on becoming a laughingstock?

"Why not? I'm a competitor," said Walker, who's making his MMA debut Saturday night. "I love competition. I've been a competitor all my life. ... At this point in my life, why not?"

In the cynicism that dominates the world today, it'd be easy to just dismiss Walker's words as a smokescreen for a hidden motive -- needing money or attention easily come to mind. Why else is he fighting Greg Nagy -- a virtual unknown who has just two pro fights under his belt in Sunrise, Fla.

However, when it comes to the 1982 Heisman Trophy winner, it's hard to doubt him. After finishing a season playing for the Minnesota Vikings, Walker qualified for the 1992 U.S. Olympic bobsled team.

Why else would he risk injury during a lucrative point in his career? Why would he push his body to new limits when he could have rested or let nagging aches heal? Yeah, it's hard to doubt his love of competition.

How else do you explain that he's a fifth-degree black belt in Tae Kwon Do? That expertise, coupled with his ridiculous workout regimen -- which includes more than 2,000 sit-ups and 1,000 push-ups a day -- seemingly should have prepared him well for his 12-week crash course in MMA training.

"This is probably the hardest thing I've ever done," the 6-foot-1, 220-pound Walker said. "This was a very tough sport for me. ... Every muscle in your body is sore."

He added that his MMA instruction was even tougher than the grueling NFL training camps he endured for 12 seasons in the sweltering heat. Walker said that in football, a play goes for eight seconds and then players have 30 seconds to rest. In MMA, athletes don't have such a luxury.

Even his Tae Kwon Do skills were somewhat neutralized, saying he had to, in essence, forget about that fighting style and enter his training with a completely open mind.

Walker, who said he's an avid fan of MMA and watching it inspired him to enter the sport, is thankful to Strikeforce for giving him a shot. For a company looking to raise its profile any way it can, this was a simple decision. In announcing Walker's signing in September, Strikeforce CEO Scott Coker said, "I flew to L.A. last month to watch Herschel train and was surprised to see his advanced wrestling and striking abilities. He's got work ahead of him."

Coker's company has plenty of work to do too. Strikeforce is the No. 2 MMA company in the United States, behind the juggernaut Ultimate Fighting Championship. Not many sports bosses are going to travel to watch a guy pushing 50. But, Walker brings a known name and will attract mainstream interest.

Strikeforce is having Walker do all the media rounds, and he's obliging. But, he's also staying the humble guy from Georgia, choosing to remain realistic.

When asked about if he aspires to be heavyweight champion, Walker said, "I started too late. My goal is to go undefeated and just take it one step at a time."

Nagy, his opponent Saturday, is only 1-1, so Walker is taking it slow -- albeit against a fighter who's 21 years younger than him and said "I fully expect to make this an event that my opponent will not include in his highlight reel."

Walker isn't afraid of getting hurt, saying no person can approach sports with a fear of injury. Whether he wins or loses, he said "I'm going to do this as long as I can."

And when his trainers tell him he's should leave the sport?

"I've got to swallow my pride and walk away."