The first time Claressa Shields and Maricela Cornejo went head-to-head, they co-starred in a YouTube video.

When it hit the internet in 2019, Shields was already a two-time Olympic gold medalist with several professional titles, including the undisputed middleweight championship. Cornejo was a seven-year veteran, but still building an online brand that encompassed boxing, fashion, fitness and self-help.

Their conversation, which appeared on Cornejo’s YouTube channel, touched on boxing, of course, but also on the two women’s shared histories as survivors of childhood sexual assault. The interview showcased both women as vulnerable, tender, supportive and sisterly; professional colleagues with the makings of close friends.

On Saturday in Detroit, Shields and Cornejo will meet as opponents, with Shields’s undisputed middleweight title at stake. The pairing highlights the close-knit world of elite women’s boxing, where bitter rivalries abound, but where boxers can be each other’s friends, fans, training partners and adversaries, often in fairly quick succession.

“If anybody wants to get in the ring and fight for my belts, I’m going to put all that friendship to the side,” said Shields, who is 13-0 with two knockouts. “This is prizefighting. It’s not friend fighting.”

The Shields-Cornejo title fight, which will headline a card at Little Caesars Arena in downtown Detroit, is the highest-profile women’s bout of early 2023, and a follow-up to the blockbuster events that vaulted women’s boxing into the spotlight last year.

Last April, a lightweight title bout between Katie Taylor and Amanda Serrano sold out Madison Square Garden. Taylor won a decision in a raucous brawl that drew 1.5 million viewers to the streaming platform DAZN, which will also show Saturday’s bout. Six months later, in October 2022, Shields defeated Savannah Marshall in a high-stakes, high-octane title bout in London. A reported two million viewers watched that fight.

Organizers of both events claim each was the richest bout in women’s boxing history, and most years either matchup would have stood alone as the single most significant women’s bout on the schedule. They featured big names, full arenas, competitive action and, not coincidentally, sustained promotion leading into fight night.

This weekend’s bout between Shields and Cornejo is different.

Cornejo, who is 16-5 with six knockouts, committed to the bout early last week, after Shields’s original opponent, Hanna Gabriels of Costa Rica, failed a doping test.

Even with a new opponent and short marketing runway, Shields’s promoter, Dmitriy Salita, views Detroit as one reason this fight could draw fans. Putting Shields, who grew up in Flint, Mich., atop a card at the new arena in Detroit also places her squarely within the city’s boxing tradition, he said.

“This is not a city where there is no boxing history. This is one of the richest boxing histories in the world,” Salita said. “The pressure that she’s under and the doors that she’s opening, every fight is a super fight for her.”

Sugar Ray Robinson spent his childhood in Detroit, and Joe Louis made the city his home base. In March 1980, three months after Joe Louis Arena opened, Hilmer Kenty, the first world champion from the famed Kronk Gym in Detroit, defended his lightweight title there. Kronk’s most famous product, Thomas Hearns, who was nicknamed the Hitman, fought in the cofeature on the same card.

Shields, 28, enters Saturday as one of boxing’s most dominant competitors of any gender. She rarely loses rounds, and has only lost two official fights in her life. As a 17-year-old amateur she dropped a disputed decision to Marshall in the lead-up to the 2012 Olympics, and in October 2021 she lost a mixed martial arts bout to Abigail Montes in the Professional Fighters League.

But as a professional boxer, Shields has won world titles in three weight classes, and has been the undisputed champion at 154 and 160 pounds. She has defeated so many champions that she has begun seeking rematches with boxers she has outclassed.

Her 2018 bout against Gabriels ended in a lopsided decision win. Salita said that if Shields wins on Saturday she might face the winner of an upcoming bout between Marshall and Franchón Crews-Dezurn, both of whom Shields has already vanquished.

The search for a stiff challenge spans sports — Shields hopes to return to mixed martial arts later this year — and every boxing division, from 147-pound welterweight to 168-pound super middleweight.

“I watch all of them, just in case they want to make that jump,” Shields said.

Saturday’s card falls at the midpoint of a busy period for high-level pro boxing. Earlier this spring, Gervonta Davis knocked out Ryan Garcia at 136 pounds, while Devin Haney squeaked past Vasiliy Lomachenko to remain the undisputed lightweight champion.

Later this summer, Stephen Fulton of Philadelphia and Naoya Inoue of Japan will meet in a super-bantamweight title fight that excites boxing purists. And on July 29, the long-delayed meeting between the welterweight champions Errol Spence Jr. and Terence Crawford is scheduled to take place in Las Vegas.

For her part, Shields was set to rematch Gabriels, when the Costa Rican contender tested positive for a steroid, clostebol. Gabriels said she absorbed the substance inadvertently, claiming it was an ingredient in an ointment she rubbed on her dog to help him heal from surgery.

Either way, she was scratched, and replaced with Cornejo, who was already training for a different bout.

Cornejo, 36, recently relocated from Seattle to Las Vegas, where she works with the renowned trainer Ismael Salas. She and Shields have one common opponent, Crews-Dezurn, who has defeated Cornejo twice.

But Cornejo enters Saturday with a three-bout win streak, and, after working with Salas, renewed confidence in her skills and tactics. She maintains a healthy esteem for Shields, but remains focused on upsetting her.

“She knows I respect her, and she respects me as well,” Cornejo said. “But when we get in a fight, it’s either you or me, honey.”