Two days before he was scheduled to try to defend his heavyweight titles against the undefeated Oleksandr Usyk, Anthony Joshua sat at a news conference on Thursday in London, his hat, headphones and even water bottles positioned to make sponsor logos visible to the cameras.

A long list of companies has invested in Joshua, the 31-year-old British boxing star: Under Armour, his apparel provider; Beats by Dre, the headphones maker; Matchroom Boxing, the promoter with which Joshua signed a lifetime contract this week. And Joshua, who is 24-1 with 22 knockouts, spoke as though Saturday’s bout against Usyk, an undefeated 34-year-old from Ukraine, was not just a contest but also an economic stimulus package. He told reporters he felt responsible for providing a platform and a payday for fighters on the undercard of an event expected to attract nearly 70,000 spectators to Tottenham Hotspur Stadium.

“I’m going to work hard, try and bring attention to boxing so it benefits everyone, not just me,” Joshua said. “I don’t promote boxing because I want to be famous. I promote it because I want everyone to benefit from it.”

The card on Saturday comes at the end of two tumultuous weeks in the boxing industry. On Sept. 11, the retired mixed martial arts fighter Vitor Belfort overwhelmed the 58-year-old former heavyweight champion Evander Holyfield in a pay-per-view bout that, depending on one’s perspective, showcased either the peak or the rock-bottom of the recent trend of novelty fights.

But over this past week, serious, competitive, meaningful fights have competed for headlines. On Wednesday afternoon, Deontay Wilder held a media conference call to hype his rematch against Tyson Fury for the W.B.C. heavyweight title, scheduled for Oct. 9 in Las Vegas. The previous day, Saúl Álvarez and Caleb Plant traded insults and blows at a news conference ahead of their Nov. 6 super-middleweight title bout.

That brawl wasn’t staged for publicity’s sake — Plant emerged with a prominent cut on his right cheek — but it did generate attention that could lead to pay-per-view sales. By Thursday afternoon, a video of the skirmish posted on Showtime Boxing’s Twitter page had been viewed 4.7 million times.

But Joshua’s main event sold without pre-fight trash talk or a news conference rumble.

Eddie Hearn, the chairman of Matchroom Boxing, said the Joshua-Usyk fight would fill Tottenham Hotspur Stadium partly because of pent-up demand. The title fight tops the biggest fight card in England since the coronavirus pandemic began, and the boxing event is the first for Tottenham Hotspur Stadium, a $1.33 billion venue that opened in 2019.

But, Hearn said, the crowd projection was also a function of Joshua’s popularity. Winning gold at the London Olympics in 2012 ensured Joshua would turn pro with a built-in audience in Britain. In April 2017, a reported 90,000 spectators watched him defeat Wladimir Klitschko at Wembley Stadium in London for the W.B.A., W.B.O. and I.B.F. titles.

“He’s the biggest star in British boxing by far, and arguably the biggest star in world boxing,” Hearn said.

Joshua’s next test is Usyk, an opponent ordered by the World Boxing Organization, and bouts between marquee champions and mandatory challengers often prompt stakeholders to think long term. A win on Saturday should position Joshua to fight the winner of next month’s fight between Fury and Wilder.

But Usyk’s résumé suggests he is not an afterthought. Like Joshua, he won Olympic gold in 2012. He turned professional as a cruiserweight and won every major sanctioning body’s title in that division. In his last cruiserweight bout, he crushed the English star Tony Bellew, and he has won both his bouts since moving to heavyweight in 2019.

“Every fight makes history,” Usyk said through a translator at the news conference on Thursday. “Me and Anthony are going to make another step in history. Something people will talk about. Something people will remember.”

The match became possible after some only-in-boxing courtroom sparring among Wilder, Fury and Joshua.

In May, Hearn said that Fury and Joshua had signed for a mid-August title unification bout. It was planned to be staged in Saudi Arabia and each fighter could have potentially earned nine figures. But Wilder sued to stop the fight, arguing that after losing to Fury in February 2020 he had exercised the rematch clause in his contract and gained the legal right to fight Fury next. A judge agreed and ordered a Wilder-Fury fight, forcing Joshua to regroup and face Usyk.

The resulting fight pits Johsua, a powerful puncher whose sometimes porous defense makes him vulnerable, against Usyk, a calculating southpaw who counterpunches with authority.

“If styles make fights, we’re in for a very, very special night,” Ed Breeze, the executive vice president of DAZN, which will stream the fight card, said at the news conference.

Similar circumstances preceded Joshua’s first professional defeat in June 2019. A scheduled title defense against Jarrell Miller fell through when Miller failed a doping test, and Joshua chose to proceed with a new opponent on the same date for his U.S. debut at Madison Square Garden. Andy Ruiz stepped in for Miller and scored a seventh-round win by technical knockout.

Joshua regained his titles in a rematch six months later, but said the Ruiz loss had taught him the value of a reset and a full training camp.

So after an unexpected change this time, instead of slotting Usyk into the August date, Joshua moved the fight to September to give it and his undefeated challenger the attention they deserve.

“It’s not complicated. If you tell me I’m fighting King Kong, I’ll give it a go,” Joshua said on Thursday. “It’s an opportunity for me to work. He’s going to work, I’m going to work.”