The year 2025 has thrown turbulent challenges at Dana White and the UFC. Even though the multi-billion-dollar promotion continues to dominate the fight industry, setbacks still strike. Over time, last-minute injuries, fighters missing weight, and canceled bouts have become part of the UFC’s ongoing drama. Earlier this year, UFC officials completely replaced the co-main event at UFC Perth, setting a precedent that would carry into UFC Rio.

As the promotion headed to Rio, the same unpredictable storm struck again. Weeks ago, Rafael Fiziev suffered an injury well before the event, forcing changes to the main card and opening the door for Mateusz Gamrot to face Charles Oliveira —a last-minute relief for Dana White amid the chaos. But today, drama hit once more at the weigh-ins at Farmasi Arena.

Valter Walker vents frustration after bout cancellation against Mohammed Usman at UFC Rio

UFC legend Kamaru Usman’s younger brother withdrew at the very last minute from his heavyweight clash against Valter Walker due to an undisclosed injury. UFC officials scrambled to find a replacement but failed, ultimately forcing the bout’s cancellation. For Valter Walker, who had been ready to take on the underdog Mohammed Usman in front of his hometown fans in Rio, fate dealt a cruel hand. The cancellation hit him hard—Walker even shed tears upon hearing the news.

But Valter Walker didn’t stop at venting on social media. After the bout’s cancellation, he exposed the Usman situation on X: “I just found out, here’s the reason for the cancellation of the fight with Valter Walker. The test that showed elevated testosterone levels was collected in September.”

At the weigh-ins, the 27-year-old Brazilian let his emotions pour out, unleashing a furious rant right on the scale in front of the commission members. In a video posted by AG.Fight, the hometown fighter breaks down in tears — heartbreak and disbelief written all over his face. Just hours earlier, he was ready to chase his fourth straight UFC victory.

The revelation about Mohammed Usman’s elevated testosterone levels has once again ignited a storm over doping control in combat sports. Elevated testosterone often points toward possible use of hormonal or performance-enhancing substances — a shadow that continues to haunt the fight game. Ironically, Mohammed’s brother, Kamaru Usman, has long been a target of similar speculation from critics. Yet, despite the whispers and accusations, Kamaru’s record remains spotless.

Kamaru Usman shares his emotions about witnessing his brother fight

Kamaru’s younger brother, heavyweight Mohammed Usman, is still carving his path. While he hasn’t yet matched his older brother’s accolades, Mohammed is steadily building his own legacy. The 36-year-old Mohammed Usman, who signed with the promotion in 2022, has gone 4-2 in his last six Octagon appearances. Mohammed, still honing his skills and gaining experience, continues to chase the shadow of the Usman name.

Reflecting on his younger brother’s journey, Kamaru Usman told BT Sports: “I’m more nervous because I don’t have control of what’s going on in there. I wish it was like a game where I could control him, but he has his own feelings and emotions and he sees what he sees. So I couldn’t control that. I’m always more nervous watching my loved ones compete, but it was an exciting moment.”

Mohammad most recently stepped into the Octagon at UFC Baku, overcoming a slow start to secure a hard-fought decision victory over Hamdy Abdelwahab and return to the win column. However, today’s sudden withdrawal puts Kamaru Usman’s younger brother in a precarious position with Dana White and the UFC, and the promotion’s next move is still under wraps.