Late last week, the path to a single, undisputed heavyweight boxing champion looked simple.

Anthony Joshua, the power puncher from London who held world titles from most of the major sanctioning bodies, was favored to win his fight on Saturday against an undefeated Ukrainian, Oleksandr Usyk. From there, a springtime showdown with the winner of the World Boxing Council title bout, which is scheduled for next month between the champion Tyson Fury and the ex-champion Deontay Wilder, seemed imminent.

But then Usyk, a former undisputed cruiserweight champion who moved up to heavyweight, outboxed Joshua over 12 bruising rounds, stunning the roughly 70,000 spectators at Tottenham Hotspur Stadium in London and upending plenty of stakeholders’ plans for the first half of 2022. Usyk, a 34-year-old southpaw, may not match Joshua’s popularity, Fury’s panache or Wilder’s punching power, but he now owns three of the four major heavyweight title belts, which means he possesses some leverage over what happens next.

Advice to any sports fan who wants to see a solitary, unified heavyweight champion: stay patient, savor the rematches and brace for plot twists.

Joshua has signaled that he will exercise his contractual right to fight Usyk again, and his promoter, Eddie Hearn, thinks that fight could happen in February or March. Usyk, a gold medalist at the 2012 Olympics in London, said at a postfight news conference that he wanted the rematch to happen at a soccer stadium in Kyiv, Ukraine. But Hearn, who is tasked with organizing the bout, says the fight will follow the money, most likely back to England.

“We will work together to maximize the revenue,” Hearn, the chairman of Matchroom Boxing, said at a postfight news conference. “Ukraine? Very unlikely.”

Although aficionados accept the proliferation of sanctioning bodies and title belts as a part of boxing, casual followers and potential fans are often, reasonably, confused by the lack of clarity over who, exactly, is the champ in a given division.

While “unified” and “undisputed” are often used interchangeably to describe a fighter who holds every major sanctioning body’s title in a given weight class, their definition changes each time a new organization emerges. In the late 1980s, when Mike Tyson ruled the heavyweight division, “undisputed” meant the possession of three titles, from the World Boxing Association, the World Boxing Council and the International Boxing Federation.

But now the World Boxing Organization exists, meaning a fighter needs to hold at least four belts simultaneously to be considered an “undisputed” champ. If a new player shows up, the unified title splinters and the dispute begins anew.

In mid-May, Fury and Hearn each announced an agreement for a midsummer bout between Joshua and Fury, with the W.B.A., W.B.C., W.B.O. and I.B.F. belts at stake. Days later, a judge ruled that Fury instead had to fight Wilder, who had filed an injunction to enforce the rematch clause in his previous fight with Fury. Although Fury and Wilder made plans to meet again, the W.B.O. ordered Joshua to face Usyk or risk being stripped of that title.

“Maybe we should have swerved him, and put the belt in the bin,” Hearn said at the news conference, indicating that a fighter of Joshua’s profile can vacate a title without losing visibility. “But that’s not what A.J.’s about.”

The upside, for fight fans, is a series of high-stakes, competitive heavyweight fights among name-brand fighters whose profile doesn’t depend on title belts. Joshua isn’t famous because he held the W.B.O. belt; the W.B.O. belt gets attention because Joshua held it.

“Would you still watch it without title belts?” Joshua asked a reporter, rhetorically, at the postfight news conference.

Oddsmakers favored Joshua, who stands 6-foot-6 and weighed 240 pounds, to retain his titles over the older, smaller Usyk. But Usyk used superior footwork and hand speed to buzz Joshua early. Joshua surged in the middle rounds, finally landing his jab, along with some heavy body blows.

By the ninth round, the damage was visible on each fighter’s face. Joshua sported a puffy right eye, and Usyk had red welts under each eye and, eventually, a cut in his right eyebrow. But Usyk upped his output in the final quarter of the fight, and he won the final four rounds on every judge’s card.

Joshua called the fight “a great experience.”

That’s a charitable way of saying Usyk took Joshua to school. According to CompuBox, Usyk landed 148 of 529 punches, compared with 123 of 641 for Joshua. Usyk also landed 44 percent of his power punches (96 of 220) while Joshua landed just 33 percent (71 of 214).

The win earned Usyk three major belts, as well as the International Boxing Organization title, which doesn’t yet fit into the “undisputed” equation. But Usyk said the upset win still wasn’t his biggest victory in London.

“London is a lucky city for me,” he said through a translator. “But not a single victory in professionals can be above Olympic gold.”