Raoni Barcelos didn’t just lose a fight at UFC Vegas 121; he absolutely terrified everyone who was watching. After a 5-round brutal back-and-forth war with rising bantamweight Raul Rosas Jr., the 39-year-old UFC veteran, during a clinch, suddenly went limp in the fifth round, slowly collapsing on the mat. What happened next was genuinely scary. The Brazilian remained unconscious, prompting medical personnel to rush into the Octagon and carry Barcelos out of the arena on a stretcher.

And now, veteran referee ‘Big’ John McCarthy has thrown an even more frightening possibility into the mix. McCarthy believes the Brazilian may have suffered an aneurysm during the fight, and he also questioned whether fans are getting the full picture of just how serious the situation could be.

“I believe he had an aneurysm,” McCarthy said on the Weighing In podcast. “You watch the way that he goes, and his arm drops, and when he goes down, he’s just slowly shutting down.

“And that’s because of the difference in pressure that’s occurring because of the aneurysm.”

There is an important caveat, however: McCarthy is not Barcelos’ doctor, and there has been no public confirmation that the Brazilian suffered an aneurysm. Barcelos’ team has said doctors are still working to determine what caused the sudden medical episode.

The UFC initially reported that Barcelos was “stable, alert, and responsive, with full movement” after undergoing a CT scan and comprehensive assessment at a Level 1 trauma center.

McCarthy, however, argued that being awake and communicating does not necessarily mean a fighter is completely out of danger.

“People are gonna sit there and give you all kinds of things,” he continued. “I’m telling you right now. You know, thank God that he’s okay at this moment. To sit there and say, ‘Oh, you know, don’t worry about him; he’s fine.’ He’s not fine.

“He is still in the ICU. There’s a reason why. You don’t keep people in an ICU because they’re fine. There’s all kinds of bad things that can still occur from this, and they’ve got to monitor him closely.”

McCarthy then went a step further. An image had reportedly surfaced showing Raoni Barcelos recovering in the hospital, but McCarthy questioned whether the picture was even real. He claimed the image may have been AI-generated.

“I saw a picture come out where they showed him in the hospital. It’s bulls—. It’s AI,” he said. “It’s a put-together photo, because the guy’s face all of a sudden is clean from having a fight like that. You saw his eye. You think his eye just healed in 18 hours?”

The former referee ultimately made a grim prediction about the Brazilian’s career.

“And look, he’s in that position, where, God bless him. I hope he’s gonna make it through this. I’m sure he is, and all the prayers to him,” McCarthy added. “But you just saw Raoni Barcelos fight his last fight.”

Still, it’s worth pumping the brakes on that conclusion as well.

Barcelos himself has since spoken from his hospital bed and reassured fans that he is doing well while undergoing further tests.

“I wanted to send you all a message to let you know that I’m okay. I’m doing very well, and I’m getting all the necessary tests done here at the hospital,” Barcelos said in a video in his native Portuguese.

His coach, Davi Ramos, has also continued to reassure fans, while Barcelos’ doctor said the fighter remains conscious, lucid, able to walk and eat, with his continued hospitalization described as precautionary. The exact cause of the episode remains unclear.

That makes McCarthy’s aneurysm theory just that—a theory. But can we blame the veteran referee for being concerned?

After all, the reason moments like Raoni Barcelos’ collapse hit so hard is because combat sports have seen just how devastating brain injuries can be.

Just last month, the MMA and boxing world mourned the death of former professional boxer Prichard Colon at just 33 years old. Colon had spent more than a decade in a vegetative state after suffering a severe traumatic brain injury during his 2015 bout with Terrel Williams.

And while Colon’s case was different from the aneurysm theory McCarthy raised regarding Barcelos, his condition stemmed from repeated illegal blows to the back of the head during the fight. But the heartbreaking story still highlights the same terrifying reality: neurological injuries can have consequences that extend far beyond the final bell.

And Raoni Barcelos’ situation also taps into a much bigger conversation in MMA: what happens to fighters’ brains once the cameras are gone and the paychecks stop?

The Dana White-led promotion classifies its fighters as independent contractors rather than employees, which has long fueled debate over who should bear the long-term costs of injuries and conditions linked to repeated head trauma, including chronic traumatic encephalopathy (CTE).

For fighters who spend years taking damage inside the cage, those consequences can potentially follow them long after retirement. But this isn’t just a UFC problem. The independent-contractor model is common across much of the combat-sports world.

Still, all of that bigger-picture debate can wait. Right now, the most important thing is Raoni Barcelos. The 39-year-old is still undergoing medical tests, and until doctors have a clearer idea of what caused his frightening collapse, the focus has to remain on his health and recovery.