On Saturday at the Scottrade Center in St. Louis, the veteran pair will do so once again in the main event of Strikeforce's latest offering on Showtime.
Regardless of the outcome, which promoters say will determine the No. 1 contender in Strikeforce's light heavyweight division, both men know they're tasked with a far easier challenge than the one that faced them Feb. 26, 2000.
Competing as undefeated talents yet to make a mark on a lost-in-the-wilderness sport, Henderson and "Babalu" found themselves in the finals of what would eventually be considered one of Japan's most influential MMA events -- Rings' King of Kings 1999 32-man tournament.
Neither man necessarily expected to take the $200,000 prize when they agreed to be part of a field that featured multiple former and future champions of the sport's most prestigious organizations. Nonetheless, there they were, inside Tokyo's packed Nippon-Budokan arena, matched after already fighting twice that night and twice more in the opening round a few months before in October, with the opportunity to earn life-changing money.
"I was kind of broke and still trying to make an Olympic team," Henderson said. "I needed the money, just the show-up money. I didn't expect to win. With it being in Japan I didn't expect the decisions to go my way."
Henderson's MMA credentials consisted of two four-man tournament titles, but he hadn't treated fighting seriously. His focus was wrestling, so much so that before accepting the King of Kings invitation he didn't spar any kickboxing.
Sobral, then a 24-year-old, 240-pound heavyweight, was happy just to get a shot in the tournament. Promoters preferred his legendary mentor, Marco Ruas, or well-known teammate, Pedro Rizzo. When they couldn't participate, Rings looked to Babalu, honed in the ways of Brazil's bare-knuckled brutality, who quickly obliged.
"To be Brazilian and fight outside the country in Japan, that was for people like Marco Ruas and Rickson Gracie," Sobral recounted.
If something was on the line other than an adult-sized trophy and oversized cardboard check, it hadn't crossed the fighters' minds simply because implications of the two King of Kings tournaments could not be known in advance. It's clear now that these events helped establish a pecking order by which future rankings and major fights would get made, just as Pride FC tournaments did in subsequent years.
Rooted in Japan's hard-style professional wrestling, Rings wasn't considered legitimate until it ramped up the prize money and the quality of fighters; it was the organizers' soon-to-be failed attempt to inject Rings into a burgeoning Japanese fight landscape alongside K-1 and Pride.
To capture the tournament, which prohibited striking to the head on the ground, a fighter was required to win five times in two events spread over four months. The route to the championship required three victories in a matter of hours. As Sobral and Henderson stood across from one another, they'd already clocked in a combined 45 minutes and 40 seconds of combat that night.
Henderson was limping after tearing a knee ligament in the semifinal, a controversial three-round split decision against future Pride and UFC heavyweight champion Antonio Rodrigo Nogueira. That came on the heels of a 10-minute stretch in which the American, then 29, tackled heavyweight Gilbert Yvel 16 times in 10 minutes.
"With the exception of fighting sick against Yuki Kondo [in 2004], that was definitely my toughest night of fighting," Henderson said.
Sobral's effort included an armbar over Russian Mikhail Illoukhine and decision against Japan's Kiyoshi Tamura. When he stepped in against Henderson, both were undefeated. Both knew how much money was on the line. Neither had any sense that winning and losing would play such a large part in dictating the course of their careers.
Henderson fought to avoid Sobral's submissions, making the championship bout a slow affair.
"I was tired. He was tired," said the 35-year-old Brazilian. "We fought for money, but it was more. It was different from today. It was more romantic."
Henderson, the only man in Pride history to hold titles at 205 and 185 pounds, earned a majority decision after two rounds, catapulting him to a Japan-based career until the sport took off in America.
Sobral's résumé is decidedly more nomadic, including stints in UFC before he was ostracized in 2007 for holding on to a choke for too long against David Heath.
"Everyone wants to win lottery money, but who knows if lottery money will be good for you?" Sobral said. "I can say it's been an amazing journey for me. I have had ups and downs in my career."
Now 40, Henderson doesn't call to mind sepia-colored visions of the night he went seven rounds against three dangerous opponents. He didn't bother watching tape of the first bout as homework for the second, since both fighters -- like the sport they compete in -- are changed.
A decade after bringing home an epic event, Henderson (25-8) and Sobral (36-8) march on. Older. Wiser. Probably a step slower. Yet the spirit that marked their first encounter remains strong.
"I was pretty close to being considered the best in the world at one point," said Henderson, who competes Saturday for the first time since losing to Jake Shields in April. "I need to get back in there and do it."
Josh Gross covers MMA for ESPN.com. Follow him on Twitter at JoshGrossESPN.