LOS ANGELES -- Shane Mosley and Sergio Mora, both Southern California natives, have experienced great moments in their careers at the Staples Center.
In the first main event in arena history, Mosley outpointed Oscar De La Hoya, now his good friend and promotional partner with Golden Boy, to win the welterweight title in their 2000 classic. Nine years later, Mosley returned and stunned the boxing world with his unexpected -- and unexpectedly easy -- ninth-round knockout of Antonio Margarito, who was caught with loaded hand wraps before the fight, to regain a welterweight title.
In 2005, Mora won the first season of "The Contender" reality show and the $1 million grand prize on NBC by defeating Peter Manfredo Jr. in Las Vegas. They had an immediate rematch in their first post-"Contender" fight at Staples Center five months later, and Mora edged him again on a split decision.
"It's always good to come back home and do some fights, especially at the Staples Center," Mosley said. "Being that Sergio Mora is from East L.A., he likes fighting at home as well. So this is going to be a night where both fighters have had great successes at the Staples Center."
But, barring a draw, only one of them will leave the ring with another fond memory and big fight in front of him. The loser's career will take a massive hit following their junior middleweight fight Saturday night (HBO PPV, 9 ET, $44.95) in the main event of Golden Boy's Mexican bicentennial celebration card.
Mosley, who is 39 and coming off a one-sided decision loss to Floyd Mayweather Jr. in May, is fighting to remain relevant. Given his age and recent performance, a victory is almost mandatory for him to continue to get any sort of meaningful, lucrative fights. And Mosley -- who is moving back up to junior middleweight, where he used to be champion -- has aspirations to fight Manny Pacquiao and have rematches with Mayweather and Miguel Cotto, who beat him in 2007.
Even with a win, that slate is unlikely. With a loss, forget it. Mosley (46-6, 39 KOs), a former three-division champion, knows he has a tough task in front of him against the naturally bigger and taller Mora.
"Yes, it could be a setback," Mosley said of losing. "Some fans take it for granted that this guy is a little bigger. He's also fast. He works very hard. He's a competitor. He loves to win. He only lost one time, and that's to Vernon Forrest, in his whole career. So he can fight. So I think people are mistaken and thinking that it's just going to be a walk in the park when it's really not.
"I have to get past Sergio Mora. I thank him for taking the fight and accepting the challenge. This guy is not someone to take lightly. He beat Vernon Forrest. I never beat the late, great Vernon Forrest. He is a competitor and he comes to win."
Three years after his "Contender" victory, Mora (21-1-1, 6 KOs) became the first alumni of the show to win a world title, outpointing Forrest -- who twice defeated a prime Mosley -- to claim a junior middleweight belt. But Mora could not keep the momentum going. He lost to Forrest in their rematch three months later and has fought only once since, a win at middleweight in May in his first fight since signing with Golden Boy and hooking up with manager Cameron Dunkin.
A win over a fighter with Mosley's fame and résumé; would surely give Mora the career boost he's been looking for. Losing, he said, is not part of the plan.
"When do I have the leisure of a loss? I think when you're talking to a fighter, they're always scared to death to lose," said Mora, 29. "They have a lot of pride and they don't want that embarrassment. Nothing else matters but to win. It's a must-win. Every fight for me is a must-win. Whenever things go well for me in camp I have no excuses like I did for this camp, I really feel that I can beat the best. So this is just another opportunity for me to prove that."
Said Mosley, "Sergio has added pressure because he feels that he has to prove to the world that he is somebody."
Mora grew up a Mosley fan and has shown respect for him throughout the promotion, but he is also confident of victory.
"Sugar Shane Mosley is someone I respect and someone I value outside of the ring. He is a legend," Mora said. "I am fighting another Hall of Famer. He has everything behind him. He has the experience, the power and the chin. He has never been knocked out and he is undefeated at Staples Center. He is the real deal."
"The stars are aligning for something special to happen on Saturday," Mora said. "It is fate, faith and destiny. People don't believe in destiny, they believe in luck. If you believe in luck, go live in Las Vegas. This is my time, and I am finally with a promoter [Golden Boy] that believes in me. When you leave Staples Center, you're going to say '[Fernando] Vargas couldn't [beat Mosley]. De La Hoya couldn't do it. Margarito couldn't do it, but Sergio Mora did it.' It takes more than speed, experience and guts to beat Mosley, and I know I have what it takes."
One of the things Mora and trainer Dean Campos said they have done during training is forget about Mosley's poor performance against Mayweather, whom he hurt badly in the second round -- but he let the moment escape and lost the rest of the fight in non-competitive fashion.
"I don't think age caught up to him," Campos said. "I just think that the inactivity [and] the style that Mayweather has is a frustrating style. Mosley likes to fight and Floyd is the type of guy that takes the fight out of the fighter. He's constantly throwing water on you every time you want to start a fire. I think it's frustrating for a guy like Mosley. I'm not saying that he's not a smart fighter, because he is, but he's a very aggressive thinking fighter and Mayweather is just the opposite. He just feeds off of the little weaknesses you have and he fights in those small little spaces and he throws you off the game.
"That could happen to anybody. We're going to see that one where he fought against Margarito. That's the guy we're going to see."
Campos said rather than dwelling on Mosley's fight with Mayweather, he's been studying some of Mosley's fights when he was in his prime.
"The Mayweather fight, that's the one I study the least," he said. "I look at all his younger days and when he was 28, 29, 30 and he was beating guys like Oscar. Those are the guys I look at, and I sort of look at what he does. I'm impressed with what I see, and hopefully we can defuse him a little bit and do some things that he's not too comfortable with."
Mosley looked lethargic and could not get off his punches after the second round, when he had Mayweather badly hurt. Mosley said he had a neck problem in that fight and vowed that if he gets Mora in the same position, he will end the fight this time.
"With the Floyd fight, it wasn't that I was tired," Mosley said. "It was just that my neck was a little tight and I couldn't throw any more punches like I wanted to. If I'm fighting the second round and I make it to the 12th round, then that says that I obviously wasn't that tired. I just got a little tight, and I couldn't throw the punches like I wanted to. I can assure you that that won't happen again."
Dan Rafael is the boxing writer for ESPN.com. Follow him on Twitter @danrafaelespn.