In a jaw-dropping turn of events, Ramón Cárdenas pulled off one of the greatest upsets in boxing history, knocking out pound-for-pound king Naoya Inoue in a stunning fourth-round finish at  T-Mobile Arena on May 4. The shocking defeat marks the first loss of Inoue’s illustrious career, ending his reign as the undisputed super bantamweight champion and sending the boxing world into a state of disbelief.

A Knockout That Rewrote History

The highly anticipated main event, broadcast live on ESPN+ and Sky Sports, pitted Inoue (27-1, 24 KOs), Japan’s “Monster,” against Cárdenas (24-1, 15 KOs), a relatively unheralded American challenger. Inoue, a four-division world champion with an unblemished record, was expected to dominate, with betting odds listing him as a -1200 favorite. However, Cárdenas, known for his durability and upset win over Eduardo Ramirez in 2022, had other plans.

The fight started with Inoue’s trademark precision, as he controlled the first two rounds with blistering combinations, landing 42 power punches to Cárdenas’ 19, per CompuBox. Cárdenas absorbed the punishment, his face swelling under Inoue’s onslaught, but refused to back down. In the third round, he began to find his rhythm, landing a sharp counter right that briefly staggered Inoue—a moment that foreshadowed the chaos to come.

Then, in the fourth round, with the clock at 2:10, Cárdenas unleashed a devastating left hook that caught Inoue flush on the jaw, sending the champion crashing to the canvas for the first time in his professional career. The sold-out crowd of 20,000 at T-Mobile Arena erupted in disbelief as Inoue struggled to rise, his legs betraying him. Referee Robert Byrd counted to eight, but as Inoue staggered to his feet, Cárdenas pounced, landing a flurry of punches that forced Byrd to stop the fight at 2:28, crowning Cárdenas the new WBA, WBC, IBF, and WBO super bantamweight champion.

Cárdenas’ Triumph, Inoue’s Fall

Cárdenas, overcome with emotion, dropped to his knees in tears as his team stormed the ring. “I told everyone I’d shock the world—no one believed in me, but I did!” he shouted in his post-fight interview with ESPN. “Inoue’s a legend, but I knew I could catch him. This is for my family, my city, my country!” The 29-year-old from San Antonio, Texas, now stands as the new face of the 122-pound division, with his $2 million purse dwarfed by the historic significance of his victory.

Inoue, visibly shaken, was gracious in defeat but vowed to return. “I made a mistake, and he capitalized—I respect him,” Inoue said through a translator, his face bruised but his resolve intact. “I’ll be back to reclaim my titles.” The loss ends Inoue’s 27-fight win streak and marks the first time he’s been stopped, a feat previously thought impossible given his reputation for durability and dominance.

Boxing World in Shock

The upset has sent shockwaves through the boxing community. On social media, the hashtag #CárdenasShocksInoue trended worldwide, amassing over 5 million posts within hours. Fans expressed disbelief, with one user writing, “Inoue knocked out?! I need to lie down—this can’t be real!” Another called it “the biggest upset since Buster Douglas beat Tyson.”

Prominent figures in the sport were equally stunned. Mike Tyson, who predicted an Inoue knockout on ESPN before the fight, posted on X, “Never thought I’d see Inoue go down like that—Cárdenas is a warrior!” Canelo Alvarez, fresh off his own victory over William Scull, told DAZN News, “I’m shocked, but that’s boxing. Cárdenas showed heart—Inoue will come back stronger.” Terence Crawford, watching from ringside, praised Cárdenas’ timing, saying on Fight Hub TV, “That left hook was picture-perfect—Inoue never saw it coming.”

What’s Next for Cárdenas and Inoue?

Cárdenas’ victory opens the door to massive opportunities, with potential unification bouts against WBO interim champ Sam Goodman or a blockbuster clash with Marlon Tapales on the horizon. Promoter Bob Arum, speaking to Boxing Scene at 10:15 AM +07, called Cárdenas “a new star” and hinted at a rematch clause that could see Inoue back in the ring by late 2025. “This upset changes everything at 122 pounds,” Arum said. “We’ll see what Cárdenas wants next, but the fans will demand Inoue again.”

For Inoue, the loss is a bitter pill, but his legacy as a four-division champion remains intact. Analysts like Teddy Atlas suggested on his podcast that Inoue might need to adjust his aggressive style, noting, “He got reckless, and Cárdenas made him pay.” A rematch seems inevitable, with Inoue likely to invoke the clause to reclaim his titles, potentially setting up another epic showdown in Japan.

A Night That Changed Boxing

Ramón Cárdenas’ stunning knockout of Naoya Inoue isn’t just a fight result—it’s a seismic shift in boxing history. The unheralded American has dethroned the sport’s most feared fighter, rewriting the narrative at super bantamweight and proving that even the mightiest can fall. As Cárdenas basks in his newfound glory, the boxing world waits to see if Inoue can rise again—or if this upset marks the dawn of a new era.