Penn (14-5-1) is one of only two UFC fighters to have won titles in two weight classes (lightweight and welterweight), half of a select club with Randy (The Natural) Couture. Including his career outside the UFC, he has fought from lightweight to heavyweight.
Penn respects Sanchez, but it's clear he sees the challenger as just someone else in his way.
"He's got some stuff that he brings to the table but I've faced all types of opponents, all types of champion fighters, all the best guys all over the world. It's just another fight, that's all it is."
While Sanchez fights for the 155-pound title, Penn is working on his legacy. He wants future fighters to say: "It's because of him, it's because of guys like this is the reason we're all making millions."
But the proud Hawaiian clearly also wants another crack at St. Pierre, who appears to have become his MMA Moby Dick. Penn, who has not lost as a lightweight since a majority decision to Jens Pulver in January 2002, is still burning from his second career loss to St. Pierre.
"I'm not looking for a welterweight bout, it's more of a personal thing with Georges St. Pierre," said Penn. "I'm not trying to become the champ of both weight classes or anything, and I have an obligation to defend the lightweight title. But if you give me the opportunity to fight him, I would jump at the chance."
UFC president Dana White acknowledges that Penn has not got GSP out of his system.
"No I don't think he has and I think if he cleans out this division, I think he's probably going to want to go back to 170 and take a run at that again. And I think he's a different human being now than he was last time they fought."
White says Penn still has a couple of lightweights to dispose off first, likely Frankie Edgar and Gray Maynard. And when he wants to take another shot at GSP, he will have to knock off a few 170-pound contenders first.
Penn, 30, returned to action in August with a comprehensive win over Kenny Florian and says there is no GSP hangover.
"I feel like I'm back, I feel like I never left."
In fact he says the Florian fight helped him rediscover his love for the sport.
"This is one great big dream that a kid had one day so I had better sit back and relax and enjoy it," he said.
Sanchez, 27, enters the fight from a different tack.
"B.J. says he's doing this for fun, well I'm doing this for other reasons," he said. "I'm doing this to survive, I'm doing this for my livelihood, I'm fighting with my heart, my soul and my passion. I'm going to give it everything I've got. And as the rounds go on, I will be stronger."
He will have his work cut out. Penn's work ethic in training - once considered his Achilles heel - has stiffened recently as he tries to stay "relevant."
"It's unbelievable what he's done in the last year . . . I mean this kid has completely changed his life," said White. "His training regimen is sicker than anybody's I ever seen in the UFC. This kid's been coasting on talent for 10 years and now he's doing the right thing. I'm proud of him."
Counters Sanchez: "B.J.'s done his work and he's hired conditioning coaches and has his diet on point and done a hard camp. I figure he's going to come in good shape but that's not Diego Sanchez shape, man. I'm a workhorse."
Sanchez (23-2) won Season 1 of "The Ultimate Fighter" as a middleweight and campaigned as a welterweight before dropping down to 155 pounds three fights ago - a move he says taught him discipline and "brought a better Diego out of me."
The San Diego-based Sanchez fights like the Energizer Bunny on speed, literally rushing his opponents at the bell.
He may want to rethink that strategy. Penn tagged Joe Stevenson seconds into their fight at UFC 80.
Sanchez, however, says he is finally ready for his championship close-up.
"I think it's my heart that gives me the win in this fight. I want it more. I've worked so hard for so long for this opportunity. And B.J.'s had it for a long time. It's been his time for a long time. ... It's perfect timing, I feel the stars are aligned right and I feel God's going to give me this one."
But Zahabi wonders if Sanchez fits the mould of those who can beat Penn.
"The difficulty with B.J. is he's almost impossible to finish, he really is. The only two guys who were able to finish him were Georges and Matt Hughes who are much bigger and stronger than him.
"A guy at 155, to finish B.J. he's going to have to be incredibly intelligent. He's a very difficult guy to take down, to submit or to knock out. Extremely difficult. And that's why it has to take heavier guys, bigger stronger guys who can break through his defence."
On paper, it is hard to see where Sanchez has the edge even though Penn says: "A fight's a fight. Anybody can lose, all I can do is my best."
Having said that, however, he adds: "I can see myself hitting him and hurting him on Saturday night."
Penn never had a chance to do that against St. Pierre at UFC 94. After being rebuffed on two takedown attempts in the first round, the bigger Canadian took him down in the second and outmuscled him on the ground. St. Pierre eventually took Penn down four times, passing his guard an amazing six times while holding him down and battering him.
While Penn used to be known for his jiu-jitsu prowess - he won the world Brazilian jiu-jitsu championship after just three years in the sport and is the first non-Brazilian to win that title at the black belt level - his striking has taken centre stage in recent years. He has landed 61 per cent of his strikes in the UFC - only middleweight champion Anderson Silva and heavyweight Cain Velasquez have a higher accuracy among fighters with at least 300 strike attempts.
He connects on 57 per cent of his lead jabs. That's more than twice as good as the average fighter and ties him with Silva as best in the UFC.
In 19 career fights, he has never been knocked down.
Sanchez too has never been knocked down. On his feet, his standup accuracy is 43 per cent. He is more effective on the ground (56 per cent), showing dangerous elbow strikes in his last win over Clay Guida.
His defence on the ground is also solid. While he has been taken down 18 times, his guard has only been passed three times.
The Memphis card has an interesting heavyweight co-main event with former champion Frank Mir taking on French striker Cheick Kongo. The matchup, which features Mir's submission skills against Kongo's sharp standup game, has become more pointed thanks to Mir's not very sophisticated trash-talking.
Elsewhere, middleweight Alan (The Talent) Belcher has a point to prove against Brazilian Wilson Gouveia in what could be one of the fights of the night. Belcher thinks he should have got the decision that went to Yoshihiro Akiyama last time out and he is upset that he has been relegated to the undercard.
Heavyweight Paul Buentello returns to the UFC after an absence of almost four years to take on six-foot-11 Swiss stringbean Stefan (Skyscraper) Struve. While fighters in other weight classes counted calories to make weight this week, Buentello has been enjoying Memphis rib joints.
Halifax welterweight T.J. Grant looks to rebound from a loss to Dong Hyun (Stun Gun) Kim at UFC 100 against a tough opponent in Kevin (The Fire) Burns.
And Florian, with Zahabi in his corner, looks to put the Penn loss behind him when he takes on the energetic Guida.
