Nearly a decade later, Georges St. Pierre still remembers the exhilaration of his first UFC fight. The future welterweight champion beat Karo Parisyan in Las Vegas at UFC 46, but that win was nothing compared to his victory over his anxieties.

“I almost stayed paralyzed in front of the crowd when I first stepped in the octagon in front of the TV (cameras),” St. Pierre said. “Even though I was fighting in a preliminary, I was very nervous. I remember it was just a feeling of the octagon that it was just something different.”

St. Pierre’s nerves have been conquered by years of training, experience and evolution into the smoothest UFC champion — but there’s always another nerve-racking challenge around the corner.

Mixed martial arts’ dominant promotion is celebrating its 20th anniversary this weekend by putting St. Pierre into what just might be his toughest fight in years. He defends his 170-pound belt against Johny Hendricks at UFC 167 on Saturday night at the MGM Grand Garden in Las Vegas.

St. Pierre is an appropriate choice for the promotion’s main event on its anniversary show. He debuted in the UFC in January 2004 and steadily worked his way to the top of the division, claiming the belt nearly six years ago and avenging his only two career losses along the way.

“I want to leave a legacy,” St. Pierre said. “To leave a legacy, I believe, is (not) only by performing in the octagon, it’s by changing things, and that’s what I’m trying to do. I’m trying to be the best I could be inside the octagon and be the good role model and the best I can be outside the octagon as well.”

St. Pierre’s approach to his sport somewhat mirrors the UFC’s evolution. What started out as a rock-’em-sock-’em, no-weight-classes, eight-man tournament at UFC 1 in Denver in November 1993 has become a corporate machine with a high-profile Fox television deal and a sport covering prime real estate among advertisers catering to young males.

Although St. Pierre is an urbane, intelligent businessman, he’s also a vicious fighter with eight consecutive title defenses. He’s determined to stay on top of his rapidly evolving sport.

“It’s harder to stay champion, because you are the target and everybody looks at you, and they want what you have,” St. Pierre said. “That’s why every time I finish a fight, I focus on the next big thing. Right away, my mind gets ready for the next big thing. I’m completely obsessed about that. And that’s one of the things I believe that is the reason why … I’ve been able to stay champion.”

UFC 167 also features Chael Sonnen’s light heavyweight bout with Rashad Evans, and St. Pierre protege Rory MacDonald takes on veteran welterweight Robbie Lawler. Welterweight Josh Koshcheck and lightweight Donald “Cowboy” Cerrone also will appear on the undercard.

Hendricks earned a shot at the Canadian champ with years of steady work of his own, including six straight wins in the last three years. Although he has never been in a five-round fight, the extra length assigned to the UFC’s title bouts and main events, the heavily bearded challenger from Oklahoma is confident he can hang in there.

“There could have been so many more people that could headline this show, and they chose us,” Hendricks said. “So it shows a vote of confidence of what we can do, how we can make this an exciting show. It’s a privilege and an honor to be on this 20th anniversary and enjoy it.”

Hendricks was an NCAA champion wrestler at Oklahoma State, but he’s considered an enormous challenge for St. Pierre largely because of the knockout power in his left hand. He didn’t start training in MMA until after college, but his striking has developed into his primary skill set.

That’s a remarkable evolution, but it’s familiar to St. Pierre, another talented wrestler who prides himself on neutralizing his opponents’ best skills. St. Pierre’s jab has grown into a formidable weapon alongside his wrestling, and no opponent in recent years has had any answer for the combination.

St. Pierre hasn’t fought in the UFC’s hometown since July 2009 at UFC 100, with his last four fights in Canada. While he has practically whitewashed several of his recent opponents in lopsided decision victories, St. Pierre realizes this fight is unlikely to be tidy.

“I believe as time goes by, the fighters get better all the time,” St. Pierre said. “So Johny Hendricks, I believe, is the best guy that I’ve fought in my entire career, and I train for Johny to prepare myself against the best guy that I ever faced.”