Even after seven consecutive victories in title fights for the Ultimate Fighting Championship, the No. 1 welterweight in mixed martial arts takes nothing for granted.

"I'm always nervous," says Georges St. Pierre, UFC's 170-pound champion. "A lot of fighters are like, 'No, I'm not nervous.' I think it's a lie. If you're not nervous, it's because you don't care about something."

St. Pierre has a title defense scheduled for Saturday at UFC 129 against Jake Shields, a former champion in EliteXC and Strikeforce. It's the main event for UFC's biggest show to date and the most significant fight of Shields' career. Yet if St. Pierre wins, it will recede quickly into the background as a warm-up for a superfight with middleweight champion Anderson Silva.

That's what happens when UFC President Dana White calls a fighter one of the two best mixed martial artists at any weight. But the focus on a fantasy bout with Silva, which UFC officials have been openly discussing for several months, annoys St. Pierre. He argues that Shields' accomplishments make him too dangerous to dismiss.

"This like a trap for me," St. Pierre, 29, says. "I have the pressure of going through Jake Shields like a knife in butter, but they don't understand the danger. … He's a very smart guy. That's why he's dangerous."

Of the top 10 welterweights in the USA TODAY/SB Nation consensus rankings, Shields has beaten three and St. Pierre has defeated four. But the challenger also has traveled paths St. Pierre has yet to try.

While UFC salivates over the possibility of its 170-pound champion moving up a weight class, Shields already has beaten bigger foes. He held the 185-pound title in Strikeforce for nearly a year, and his victims include that brand's light-heavyweight champion, Dan Henderson, and UFC's No. 1 contender at middleweight, Yushin Okami.

In fact, the year he spent fighting at 185 pounds in Strikeforce hurt Shields in his UFC debut last October against Martin Kampmann. Shields struggled to a decision victory and then blamed his lethargy on a bad weight cut.

"I just did it too last minute, and the muscle didn't come off as fast as I thought," Shields says. "I made a huge mistake there, but my weight's down in place now."

He started shedding pounds much earlier this time. Shields weighed 182 pounds last week, which would make him smaller than St. Pierre, who normally weighs in the mid- to high 180s before official weigh-ins.

Backers of Shields contend his approach to jiu-jitsu makes it difficult to prepare for him. Former light-heavyweight champion Chuck "The Iceman" Liddell, who has trained with Shields in the past, argues Shields' takedowns, which he says are awkward, give him an edge compared to the more traditional wrestlers St. Pierre has beaten.

Shields has a reputation as one of the most dogged fighters in MMA when it comes to going for takedowns. Once he's on top, Shields holds positions better than almost anyone; Henderson and Okami are among MMA's most highly regarded wrestlers but had a hard time escaping from beneath Shields in their decision losses.

Previous opponents of St. Pierre, such as Josh Koscheck, stopped fighting aggressively after absorbing strikes from the champion, Shields says.

"Koscheck, once he got busted up a couple of times, kind of let GSP dictate the pace," Shields says. "That's what he likes to do, and that's why it's so effective. That's what I don't plan on letting him do."

St. Pierre has a clear edge in stand-up fighting over Shields, who uses striking as little more than a setup for his attempts to clinch. Yet for all of Shields' accolades, his wrestling generally gets less attention than St. Pierre's.

The champion has won several fights by turning them into the Ultimate Takedown Championship, a term derisively coined by former champion BJ Penn after spending the bulk of two rounds helpless beneath St. Pierre in their 2006 encounter. St. Pierre's 78% success rate on takedown attempts leads UFC.

These days, St. Pierre takes as much pride in his ground game as anything else.

He points to victories against top-10 welterweights Thiago Alves and Jon Fitch— fights that featured St. Pierre's ability to seamlessly blend striking and wrestling — as among his favorite performances.

"I like my fights with Alves and maybe Jon Fitch," St. Pierre says. "There's a lot of stuff I had done in that fight that was beautiful."

By Sergio Non, USA TODAY