Saturday night is the last chance for Junior dos Santos and UFC heavyweight champion Cain Velasquez to become rivals. It will be their third fight in three years, a heavyweight title trilogy in name, but it feels nothing like one in practice. Heavyweight title trilogies are the most poetically organic and evocative narrative in combat sports: When done right, they are a trio of fights that come to define the careers of two men and one stretch of time in its corner of history. 

Floyd Patterson and Ingemar Johansson traded 13 knockdowns over 14 rounds of boxing between 1959 and 1961 and kicked off the golden age of heavyweight boxing. Muhammad Ali and Joe Frazier made themselves into archetypes of bitter rivalry with their trio of classic fights in the early 1970s. Two decades ago, Evander Holyfield and Riddick Bowe were the perfect encapsulation of boxing's last great era, in that I'm certain David Lynch directed the whole thing. By those standards, Velasquez and dos Santos fall desperately short on admission.

It's no statement on their value as fighters, since both are undeniably the two best heavyweights alive by both skill and success. Dos Santos is a testament to the line of thinking that suggests efficient simplicity is the solution in a sport as complex and utterly chaotic as MMA. There are no surprises with dos Santos; He's a precise, fluid striker whose fast hands and double-fisted knockout power are inescapable, an event horizon. Fight dos Santos and he'll make you strike with him. Strike with dos Santos and he'll knock you out. It's that simple and that effective. 

Velasquez could not be more different. Where dos Santos strangles the chaos, Velasquez embraces it. Watching him fight is never anything less than jarring -- a burly, barrel-chested, 240-pound brick who fights at a pace unsustainable for everyone but him. He is good at everything and can do everything faster and much longer than anyone else can. This approach is radioactive in its unfailing ability to overwhelm opponents by mere exposure. Like being locked in a room made of polonium, it's all just a matter of time. 

Their two styles form a kinetic point-counterpoint debate, or at least that was the expectation going into their first fight in November of 2011. Unfortunately, it turned out to be a fight that never should have happened. Promised to Fox as the main event of the UFC's flagship network debut, Dana White and company quickly learned you can't break your first promise after signing a seven-year deal worth $700 million. Dos Santos suffered a torn meniscus with the fight a week and a half away, while Velasquez battled shoulder issues all through training camp before tearing his anterior cruciate ligament just days before the weigh-in. Normal circumstances would have demanded a cancellation, but there was no cancelling the main event of the UFC's introduction to mainstream viewers. The fight went on, and it wasn't much of a fight.

Dos Santos looked leaden and tentative while Velasquez, the reigning champion, hobbled at half-speed. An awkward overhand right landed for dos Santos and was followed by coffin nail punches on a downed Velasquez that ended the fight after just 64 seconds. The fight was an anticlimactic disappointment on its own merits. Once word leaked of the injuries both men fought through, the fight became a pointless spectacle in retrospect. Not even the inevitable rematch could fix that.

Said rematch was scheduled for December of 2012, seven months after Velasquez and dos Santos posted dominant victories on the same card. There were no pre-fight whispers of injuries or botched training camps this time around, and so it seemed the two best heavyweights of our time would put on the classic fight that felt like the only righteous outcome. What we got instead was a five-round-long Velasquez highlight reel. Nearly knocked out in the first frame, dos Santos spent the remainder doing more surviving than fighting. Rounds played out as a Möbius strip of dos Santos scrambling on his back foot as Velasquez collapsed the pocket with an endlessly effective variety of strikes and takedowns. Dos Santos never had room to breathe, never mind room to get off an effective strike. The title went back to Velasquez.

Six months later, both men again posted dominant victories on the same card. In a thin heavyweight division, the only legitimate challenger for Velasquez remains dos Santos. The only question is if this is the fight where they get on even terms. The trilogy demands narrative satisfaction, but the only route there ends with another dominant Velasquez win -- the least satisfying outcome possible. A trilogy without a classic fight or even a competitive one makes no sense. However, the reason this trilogy doesn't make sense is that this isn't a trilogy. While it is the classic model for combat sport rivalries, it's not the only one.

To call the heavyweight kickboxing of the mid-to-late 90's a golden era is to realize the term doesn't always live up to the reality. K-1 was the premier kickboxing organization in the world at the time, and their peak coincided with a boom in heavyweight talent. And no one was more talented than Ernesto Hoost, the Sugar Ray Leonard of heavyweight kickboxing, if you can imagine such a thing. Hoost's nickname, "Mr. Perfect", sums up his technical mastery, but doesn't begin to cover the speed with which he operated and the leather-bound durability that kept him upright against Peter Aerts, his greatest rival.

Aerts was a wall of a human at over six-foot-three and 240 pounds, and he hit every bit as inhumanly hard as you'd expect. He also shared the Dutch kickboxing pedigree of Hoost and it showed. While his 79 career stoppage wins overshadowed his pure technical skill, opponents knew that Aerts was both a knockout artist and a patient, calculating strategist.

The two men fought five times as part of a rivalry that spanned three decades and went to Hoost on a three-to-two tally. Another great K-1 champion of that time, Andy Hug, fought both men four times, splitting the series with Aerts and going one-for-four against Hoost. This entire era of heavyweight kickboxing is defined by longform rivalries that make table-setting out of trilogies. Both Velasquez and dos Santos should expect the same of themselves.

After all, there is no one else for them to fight, at least not right now. The heavyweight division is painfully thin, and there is no wave of top prospects peeking over the horizon. They'll keep on beating everyone there is to fight and leave the UFC no choice but to keep on matching their two best heavyweights. This may not provide the cohesive narrative of a true trilogy, but it does offer something far better. 

Sports are supposed to be about the best going against the best, because no one lines up en masse for mediocrity. We may never get a competitive fight between Velasquez and dos Santos, but we will get a fight between the two best heavyweights in the world regardless. As long as that's still the case whenever Velasquez and dos Santos fight, nothing else matters.