This weekend, while small clusters of boxing fans from around the world gather to watch one of the most highly anticipated  boxing matches of the past decade, most sports fans will turn a blind-eye to the competition, not because they're uninterested or don't care, but rather, because boxing just isn't promoted in the same way it once was.

Boxing fans were reminded of this fact upon the announcement of the death of Joe Frazier, one of the all-time great heavyweight fighters, a former gold medal Olympian and world champion that famously battled Muhammad Ali in the greatest boxing trilogy ever.

More than 30 years later, Ali-Frazier is still the preeminent reference point for any great boxing trilogy. After their bouts, Ali and Frazier were forever tied to each other, like two stars tightly orbiting each other as they flew through the cosmos until they inevitably fizzled. Even in death, Frazier is most remembered for his hard-fought battles against Muhammed Ali, a fact noted in most obituaries written about him in major media outlets. Ali defined Frazier, and Frazier defined Ali. They were each other's greatest opponents and also each other's greatest triumphs. That's what the boxing trilogy is about.

It's not often that fans get to see a great boxing trilogy in the modern era of the sport. Fan favorites such as Floyd Mayweather Jr., Oscar de la Hoya, or Mike Tyson have had several great fights, but in the span of their wildly successful careers, they've failed to find that one person — the perfect counterbalance — that challenged them so closely the first time, they had to fight again — and then again.

The boxing trilogy is one of the most important affairs in the entire sport. It embodies all the operatic waves that make boxing great: triumph, redemption, resilience and perseverance. It's about several rounds of brutal, technical and romanticized violence. By the third fight, it's rare that either boxer will need to finish the trilogy for money or notoriety. The third fight is taken for pride. It's taken to settle a score that, undoubtedly, defines two fighter's careers. And as we've seen with Joe Frazier, a great boxing trilogy will define a fighter even in death.

The boxing trilogy always begins the same way: the first fight is highly anticipated and, once the first bell rings, the fight exceeds most people's expectations; after losing a close fought battle, the losing fighter and the blood-thirsty public demand a rematch; in the second fight, the loser of the first fight battles back to earn redemption — this sets up the trilogy.

In the final fight of a great boxing trilogy, the boxers are never the same as they were earlier in their careers. They're not as quick. They're not as young. But they're just as dedicated to proving to themselves and the public that they can be triumphant when the lights shine brightest and when all odds are against them. Great fighters cement their place in boxing history during the last fight. It is the moment they will forever be judged by. Even in death.

It's been a long time since boxing fans have been able to witness a great trilogy. The last was started in 2000 and ended in 2004. It was between Marco Antonio Barrera and Erik Morales, two great lightweight Mexican fighters. In an era when boxing was largely overlooked by the general sports-watching public, Barrera and Morales dazzled viewers. Many boxing analysts referred to them as the Ali and Frazier of Mexico. Their rivalry was deep-seeded and their fights were long, arduous, blood-soaked wars. After these two stars met, they would never, ever, be the same. And as with Ali-Frazier, in death, Barrera and Morales will always be remembered only in comparison to their greatest foe.

Manny Pacquiao and Juan Manuel Marquez will fight for the third and final time this weekend, on Nov. 12. It will likely be bloody, technical and thrilling, with somewhere near 100 punches thrown each round from each fighter. It's rare that the paying public gets to see that much action from a pay-per-view fight, and boxing fans are sure to relish every moment.

Neither Pacquiao nor Marquez needs this fight for money or notoriety. The two will fight this weekend because that's what they do. That's what they've done for well over 20 years each, and it's what they do best. They'll fight just to fight. Although each boxer is sure to earn a large sum of money from the event, they'll fight for their pride — their legacy.

Without blood, there is not fight, said Marquez in an episode of HBO's 24/7, a reality television show that follows the fighters around in the weeks prior to the fight. He hasn't beaten me yet, and it's like a thorn in my side I want to pull out.

While Marquez may not believe that he lost the first two fights, the official rulings tell a different story. Marquez has been knocked down four times in his first two fights against Pacquiao, only to rise to his feet on every single occasion. In their first fight, Marquez fell to the canvas three times in the first round, stood each time, survived the round and fought back and earned a draw. In their second fight, Marquez lost to Pacquiao by one point.

Marquez aims to prove to everyone, including Pacquiao, that he has the intelligence and the fortitude to withstand and defeat Pacquiao's blinding hand-speed and supernatural strength. Pacquiao, meanwhile, aims to knockout Marquez in order to prove that he's won every match prior to this third fight.

Fights like Pacquiao-Marquez III only occur every ten years or so. In the modern era, it takes several years, several fights, for the sport to filter through the less dedicated, less macho, boxers that fill a large majority of space in the sport. After years of filtering, it takes two great fighters to make two great fights in order to get the third.

Boxing trilogies are a cosmic coincidence. There are almost an infinite number of variables that can prevent the trilogy from being completed. It takes two amazing, hard-to-judge fights before the third can actually be made. When the third is made, it's always a historic event.

Pacquiao-Marquez III will not only live up to the hype, because both fighters are willing to take lots of risk, but because they relish in the riskiest moments. They throw a high-volume of punches and don't mind getting hit in the head several times in order to dish-out one powerful blow. They're each intent on proving the other wrong, and, in the end, they'll prove to us all that they're two of the greatest fighters of the modern era.

For those that sit back and wait for Mayweather to fight Pacquiao, don't expect as much action in that fight if it ever happens. Pacquiao-Mayweather would be one of the most technical fights of all-time. But it's unlikely that Pacquiao, if he does fight Mayweather, would do it twice, let alone three times.

Regardless of whether Pacquiao ever fights Mayweather, Pacquiao-Marquez III will be the most important fight of our era. It is the culmination of the trilogy. The final fight that will close the book on one of the most wild chapters in Pacquiao's career. Enjoy Pacquiao-Marquez III while it lasts because these things don't happen often.