LAS VEGAS — Dmitry Bivol sat at the crowded head table, between his manager, Vadim Kornilov, and his promoter, Eddie Hearn, and beamed as he addressed reporters in a packed room at T-Mobile Arena late Saturday.

Bivol, the World Boxing Association light-heavyweight champion, looked virtually the same after 12 punishing rounds against Saúl Álvarez as he did before the fight began. His dark brown hair was cut close and brushed forward. His face was unmarked.

Only his demeanor had changed.

At a news conference last week, Bivol had glared coldly at Álvarez, the undisputed super-middleweight champion and unquestionably the headliner Saturday night. But after beating Álvarez, who is known as Canelo, by unanimous decision, Bivol, who grew up in Russia, was smiling as he fielded questions in English, his second language.

“I enjoyed the fight,” he said. “I heard a lot of the fans yelling. It motivated me.”

The outcome qualified as an upset for most people involved, including Álvarez’s supporters, especially those who had come to Las Vegas. Leading up to the fight, Álvarez had mused about defeating Bivol and eventually becoming the undisputed light-heavyweight champion.

Álvarez’s business partners, including DAZN, the streaming service that used Saturday’s bout to begin its pay-per-view service, and Matchroom Sport, the promotional outfit that supplies DAZN with boxing content, were also jolted by the outcome.

Álvarez said he wanted an immediate rematch, and a business case can easily be made for a second bout with Bivol. Despite the loss, Álvarez, whose record is 57-2-2, remains boxing’s biggest single attraction. A match with him is a windfall for anyone involved.

But Bivol, who is 20-0 with 11 knockouts, also introduced a competition-based argument for moving on from Álvarez.

“My dream is to be the undisputed champion,” he said.

Through Kornilov, who interpreted when Bivol, 31, spoke Russian, the boxer said an Álvarez rematch would depend on his receiving “what I deserve.”

The comment was a shorthand for money, and a lot of money circulates when Álvarez, who is also 31, fights.

In 2018, Álvarez was the centerpiece of a $365 million deal between DAZN, which was just starting up in the United States and entering the boxing market, and Golden Boy, the company promoting him. Álvarez split with Golden Boy, and, as a promotional free agent, teamed with DAZN and Matchroom on a series of bouts in which he unified titles in the 168-pound super-middleweight division. Last November, Álvarez jumped to Showtime and defeated Caleb Plant to become undisputed champion.

Álvarez received a $40 million guarantee for the Plant bout. He made $15 million upfront for fighting Bivol, the smaller guarantee a hint that organizers expected robust pay-per-view sales — and a lucrative bonus for the headliner.

For its part, DAZN has long planned to arrange a third match between Álvarez and Gennady Golovkin, the middleweight champion, who has also teamed with the streaming service. Their first two bouts, a draw and an Álvarez win, attracted 2.4 million combined pay-per-view buys, attractive numbers for DAZN, which now charges subscribers a premium for Álvarez bouts.

But Saturday night’s result could delay an Álvarez-Golovkin trilogy. Again.

“I think Canelo and Dimitry Two is the biggest fight in boxing right now,” Hearn, the chairman of Matchroom, said of an Álvarez-Bivol rematch.

On Saturday night, all three judges scored the bout 115-113 for Bivol. They all awarded each of the first four rounds to Álvarez, then had Bivol winning seven of the remaining eight. According to Compubox, Bivol landed 152 of 710 punches, while Álvarez threw 495 and landed 84.

But those numbers obscured Álvarez’s game plan, which included pounding on Bivol’s left shoulder and biceps to sap the strength from Bivol’s jabs and left hooks. Those swings didn’t count as landed punches, but they did have an impact. By Round 7, Bivol’s upper left arm had turned bright red.

Bivol kept using his left hand anyway, spearing Álvarez with jabs to the body and head. Finishing five-punch combinations by throwing left hooks also had an effect the statistics could not measure. When Bivol would throw a punch, Álvarez would lean back, and Bivol’s fist would whistle past his chin. The punches did not always land, but they put Álvarez out of counterpunching position, and allowed Bivol to re-establish his preferred range.

“I was the counterpuncher today,” Bivol said.

Late in the bout, when previous Álvarez opponents had faded, Bivol kept punching. In Round 11, he landed a jab, then a right hand that sent sweat flying from Álvarez’s head. In Round 12, another stiff jab forced Álvarez to retreat and regroup. He was breathing heavily by then, drained after investing his energy in power punches that had not stunned Bivol.

“He threw only hard punches,” Bivol said in English. “After hard punches, he a little bit tired. Tired, tired.”

The loss was Álvarez’s first since September 2013, when Floyd Mayweather Jr. beat him by decision, but it does not necessarily diminish him. Before the fight, Álvarez acknowledged Bivol would be much tougher than previous opponents, and afterward he said gaining weight to fight as a light heavyweight might have slowed him.

“I feel proud. I got out of my comfort zone,” Álvarez said. “I don’t feel ashamed because I look for challenges that other people don’t because they’re scared to lose.”

From here, Álvarez could invoke the rematch clause in his contract with Bivol or defend his titles at 168 pounds.

And two big obstacles stand between Bivol and fights for the undisputed light-heavyweight title.

First, Artur Beterbiev, who holds the World Boxing Council and International Boxing Federation titles, and Joe Smith Jr., the World Boxing Organization champion, are signed to Top Rank. A deal with either of them requires cooperation between promoters that happens only sparingly in this sport. Álvarez, in contrast, has one more bout on his short-term contract with DAZN and Matchroom.

Second, an Álvarez rematch will pay him better, especially now that Bivol has the one credential he did not have heading into Saturday’s bout: a win over the biggest name in boxing.