What happened to Raoni Barcelos at UFC Vegas 121?

Raoni Barcelos collapsed near the fence and became unresponsive during the fifth round of his UFC Vegas 121 main event bout against Raul Rosas Jr. at the Meta Apex in Las Vegas, Nevada. Medical personnel quickly entered the Octagon to treat Barcelos, who was subsequently taken to a local hospital where he was reportedly awake and conscious.

While the definitive cause of the collapse remains unclear, there was no obvious knockout strike immediately preceding the incident. Sports medicine physician Dr. Brian Sutterer noted based on video footage that doctors might investigate non-knockout factors, including severe exhaustion, dehydration, electrolyte abnormalities, or cardiac issues.