It took decades for anyone to touch the popularity and raw virility of 1800s champion John L. Sullivan. Variations of the phrase, “Let me shake the hand that shook the hand of John L. Sullivan,” likely uttered in earnest at one point, were even turned into one of the era’s most famous vaudeville tunes.

There is something incredibly familiar about forever chasing moments in time that are long gone in an attempt to create what can no longer be. For boxing fans who grew up in the 1980s, Mike Tyson was supposed to be the antidote to claims that modern heavyweights were no good.

Tyson’s speed, precision and aggression shocked TV audiences and those paying to get an up-close look, and by unifying the heavyweight titles he brought an end to a turbulent yet boring era for the division. His reign couldn’t survive into the early '90s, however, and when James “Buster” Douglas beat incredible odds to knock out Tyson and nab the throne newfangled heavyweights were called into question once more.

Before Douglas-Tyson, which remains one of the biggest upsets in sports history, “Iron” Mike brought his record to 37-0. Despite the young champion’s life being pure tabloid fuel, pundits wondered if Tyson could reach or even surpass the pristine 49-0 record of 1950s heavyweight champion Rocky Marciano.

James Jeffries, late 1890s and early 1900s heavyweight champion, initially retired at 19-0-2 before losing to Jack Johnson in an extremely ill-advised comeback. Larry Holmes came within one victory of matching Marciano when he lost to Michael Spinks. Tyson, and heavyweights before and after him, racked up losses preventing them from retiring undefeated as the heavyweight champion like Marciano did.

Marciano’s appeal extended beyond an unbeaten record, though, and his style and his attitude for interviews were emblematic of his era. In the emerging TV age, athletes were to play hard and be competitive but remain clean-cut and humble. The public extended Marciano the pugilistic courtesy of believing a heavily muscled maniac with homicidal intentions could be the consummate nice guy. He was an updated Jack Dempsey.

Critics of Marciano’s record pointed to aging and smaller heavyweights he defeated, but in the meanwhile fighters continued to pursue his record. About a decade after Tyson’s unsuccessful bid, a curious heavyweight from Denmark, Brian Nielsen, fought to a record that threatened to overtake “The Brockton Blockbuster.”

In 1999, Brian Doogan of The Ring wrote: “What Mark McGwire did [in 1998] to Babe Ruth and Roger Maris, Brian Nielsen is about to do to Rocky Marciano. Except McGwire actually hits against major leaguers. After reaching 49-0 with a fourth-round knockout of a guy who used to be a decent heavyweight when in shape, Tim Witherspoon, Danish heavyweight Nielsen is about to eclipse The Rock’s symbolic unbeaten milestone. How can we be so sure? Because no one with a remote chance of beating him will be allowed near the Dane, that’s how.”

As if on cue, Nielsen lost his next bout against unheralded Dicky Ryan. Perhaps even daring to invoke Marciano’s name while carefully navigating the fringes of the heavyweight rankings carried with it an embarrassing curse.

By 2001, the next best thing to retiring undefeated as heavyweight champion was leaving the sport having beaten every opponent and avenging any pro loss. Lennox Lewis, who got revenge for his only previous loss to Oliver McCall, sought to reclaim the title knocked away from him by Hasim Rahman, and Tyson loudly called out the winner of their upcoming rematch.

The groundwork for a fight between Tyson and Lewis in particular had been laid years before, when they sparred and worked out together in Cus D’Amato’s gym. D’Amato allegedly predicted the two would someday fight for the heavyweight title, but losses, injuries, prison time and more always derailed Lewis-Tyson.

Tyson struggled to shake off bad publicity from biting Evander Holyfield twice in their 1997 rematch, and even after being gifted a license to fight again, controversy found him in every fight. Whether it was trying to break Francois Botha’s arm in the clinch, hitting Orlin Norris after the bell or testing positive for cannabis after running Andrew Golota out of the ring, late-90s, early '00s Mike Tyson fights were more about confirming his stature as a draw than they were about actual boxing competition.

Boxing writers opined that Tyson could potentially defeat top heavyweights and challenge for the throne once again, just not the way he’d been looking. Tyson himself questioned his readiness, obviously aware of how chaotic this 3-0 comeback (with 2 no-contests) was. It’s just that money was far more important than anything else.

After years of financial mismanagement, Tyson needed paydays as often as he could get them. A winnable fight with the potential to have Tyson capitalize off the villain role he’d played in recent years would be ideal, and Nielsen just happened to be available.

In the summer of 2001, Tyson’s manager Shelly Finkel announced a September fight with Nielsen at Parken Stadium in Copenhagen, but Tyson's back spasms that delayed the fight a month, to October 13, 2001, 25 years ago today.

Nielsen’s Olympic bronze medal in 1992 and his subsequent dedication to bringing heavyweight boxing to Denmark made him a popular figure in his home country, where a number of his fights were scrutinized and at least one was reported to have been “fixed.” He was too heavy for his height and often entered fights out of shape, but he was also an everyman who could be seen out at a restaurant or pub and didn’t see himself as a celebrity.

In the ring, Nielsen was faster than one might expect and actually had good footwork in his earlier pro years. He also avenged his only pro loss and defeated a few ex-champions. Unfortunately most of his major fights were carefully timed and the opponents selected in such a way that would preserve Nielsen’s record.

Tyson arrived in Copenhagen about 10 days before the fight and entertained local media with a few mildly threatening quotes, and kept the training light, too light, as he weighed a career-high 239 pounds. Nielsen, who occasionally scaled in for fights under 240 pounds, also came in heavy at 259.

Nielsen’s ringwalk memorably featured the Monty Python song “Always Look on the Bright Side of Life,” while Tyson walked into “Ambitionz az a Ridah” by his deceased friend Tupac Shakur while about 20,000 in attendance waited for their own personal heavyweight spectacle.

If Tyson didn’t at least offer slices of his old self from time to time, he wouldn’t have still been any sort of attraction beyond the grotesque. But as he had in a number of his recent fights, Tyson exited his corner in the opening round looking to throw combinations and end the fight early. Nielsen absorbed body shots and enough punches upstairs to confirm a solid beard. In Round 2, Tyson backed off enough to conserve energy, which he used to send Nielsen backwards and into the ropes for a knockdown in Round 3 with a quick combination.

Bleeding from near his eye and looking bruised, Nielsen got up from the canvas and survived with the help of a low-blow break. From Round 4 forward, the pace deteriorated to Tyson doing what he could to time big punches, mostly missing, and Nielsen absorbing them between clinches while the cut and swelling near his left eye worsened.

After a tough Round 6 for Nielsen, the Danish heavyweight gave up in his corner, claiming he couldn’t see. Nielsen later said he thought repeated headbutts from Tyson during the fight led to his defeat. Tyson wasn’t impressed, either.

Tyson said: “I had no idea he was that tough. I didn’t have an easy night.”

The following month, Lewis scored a brutal knockout of Hasim Rahman, bringing the prospect of Lewis-Tyson back once more. Tyson’s inability to close the show against Nielsen should have been the clearest indication possible of how the fight would go, never mind believing Nielsen could prepare him for Lewis’ onslaught in the first place.

But nostalgia is powerful. These days they line up to shake the hand of Mike Tyson, Lennox Lewis, and in Denmark, Brian Nielsen.