Throughout her 10 years in the pros, Claressa has moved up in weight, back down again and all the way to the top of the available limits to find the toughest opposition to prove her hypothesis that she is the Greatest Woman Of All-Time. The tougher the challenge, the greater the reward, the bigger boost to the resume and the greater the chance that the often fickle boxing public will agree that she is not simply an anomalously talented outlier feasting on a still-budding field, but one that just happens to be head-and-shoulders above her otherwise talented peers.

As years have gone on, more of the public has seemingly drifted closer to the latter conclusion as they have not just seen her thoroughly dominate, but also persevere in moments when she was doubted. Christina Hammer and Savannah Marshall in particular gained traction as potential derailers of the Shields train, but turned into her most celebrated victories instead.

But as Shields has reached the limits of where she will go weight-wise, it comes all the way back around to the woman who was potentially her greatest challenge all along: Franchon Crews-Dezurn.

The two will battle for Shields’ undisputed women’s heavyweight crown Sunday in Detroit atop an event streamed on DAZN a decade after the two turned professional against one another.

While an enormous number of women deserve praise for their contributions, if one had to choose a Big Bang moment for the modern era it would be around 7:30 p.m. ET on November 2016, the second Shields and Dezurn met in the middle of the ring at T-Mobile Arena in Las Vegas and started exchanging punches.

The fight was part of a live streamed and free-to-air undercard prior to Andre Ward-Sergey Kovalev I, three months after Shields won her historic second consecutive Olympic gold medal. Rather than face any number of opponents who she could have wiped out with ease, in need of a short-notice opponent, she chose Crews-Dezurn.

Although Shields had defeated her three times in the amateurs, Franchon was still a an eight-time U.S. national amateur champion and four-time National Golden Gloves winner. In nearly all cases, blue-chip prospects such as Shields are not matched competitively in their pro debuts, let alone against a fellow decorated amateur. Even less frequently would a fighter with 12 or so national titles and two Olympic alternate trips debut as a B-side, as in the case of Crews-Dezurn.

But they are anything but normal, as viewers would find out right away that night. For a not insignificant number of those tuning in, it could have been the first time they had ever seen women’s professional boxing. For all intents and purposes, it had been absent from cable TV and premium cable for almost two decades.

Though women’s boxing had enjoyed international attention for the first time as an Olympic sports in 2012, the new faces it had revealed weren’t truly given the runway to the professional ranks until that amateur eras brightest stars, Shields and Katie Taylor, forged the trail.

So when Shields and Crews-Dezurn fought that night, they were also setting the benchmark for many in the world who would start paying attention to women’s boxing for the first time as to what it was going to be like.

It's a setting of standards that both women undertook in the U.S. amateur system as well. Crews-Dezurn was already established on the amateur scene by the time a teenaged whiz version of Shields came around, and assumed a mentor role for many women in the U.S. Olympic program. In many ways, Shields took what Crews-Dezurn did to another level with World and Olympic gold, though it remains a cruel historical footnote that if light heavyweight had been included in the initial rollout of weight classes Crews-Dezurn might have Olympic metal in her hefty trophy case as well.

On the eve of their pro debut, Dr. Christy Halbert, US Olympic coach penned an editorial for The Outside Game, which lends perspective on the boxing world the two women entered, how it changed but also how little of their interpersonal dynamic has changed in the last decade.

“As a former team coach of both women, my first reaction was that professional boxing didn’t deserve these two shining stars. Women pro boxers are notoriously underpaid and undervalued. Women’s pro fights are rarely advertised or even televised. While fight fans report enjoying women’s boxing, promoters are slow to give women athletes their just due. Any pro women boxers making a living in the sport have done so by benefitting from hefty sponsorships. But if this is what they want, then I embrace their choice, and if anyone can make positive changes in the pro game, it’s Claressa and Franchon,” wrote Halbert.

"Amateur boxing, especially USA Boxing, owes a debt of gratitude to both of these athletes, for bringing their best to Team USA, elevating everyone’s game in the amateurs, and for serving as role models for boxers for generations to come. In sport, champions can only be created if they have worthy opponents. These two have not only served each other as opponents, they have made each other better. As a former Olympic coach, I selfishly wish they’d stay on as amateurs and earn more international hardware for Team USA. But these days that world seems too small for two women who have helped shape Olympic-style boxing.”

They have made each other better.

For the better part of the last decade, Shields has been women’s boxing’s Main Character, and has seldom ceded top spot on any outlet’s women’s Pound-For-Pound list, including this publication’s. She has been undisputed in three weight classes, a world champion across five. The number of fights in which she has so much as lost a round is lower than the number of divisions she's won a world title. But amidst the massive shadow Shields has cast, Crews-Dezurn has amassed a tremendous career of her own, including two unified world championship reigns— one still ongoing at super middleweight — and reign as Ring Magazine and undisputed 168-pound queen, too.

Thoughout the years, at various points, the two have been stablemates with Salita Promotions and fought on the same events. The two have maintained a close friendship, and a collaborative one as well, all the way down to some of Shields’ ring attire being sewn by Crews-Dezurn.

They have often sparred one another — what better work could there be out there for either of them? — leading Shields in particular to remark prior to fights that those had been more difficult than the fight she was about to have. As Shields said in December of Crews-Dezurn, “(She) hit me harder than anybody, man or woman.”

At least for now, something in their friendship has fractured, if only the thin force field that keeps competitors at bay. But eventually, in search of worthy opponents, to reuse Dr. Halbert’s phrasing once more, Shields was always going to have to come back to Crews-Dezurn. And as a decorated champion and one of women’s boxing’s finest ambassadors, Crews-Dezurn has always deserved her night at the top of the bill, on the biggest stage, a chance to measure herself against the G.W.O.A.T. once more.

After four rounds 10 years ago, and hundreds more that were never seen, the bell was always going to have to sound for these two one more time.