He then suffered further embarrassment by losing via a third-round submission, before his day got even worse. His former jiu-jitsu coach Rodrigo Botti allegedly assaulted the welterweight in the lobby of his hotel, hitting him from behind, according to MMA Fighting.
However, Botti obviously hadn't thought through his getaway plan. A member of Brown's entourage chased him outside and started laying into him, taking him to the ground and repeatedly punching him in the head.
UFC officials had to restrain the men until police arrived. The incident was filmed and uploaded to YouTube.
The UFC released a statement confirming Brown escaped unharmed from the attack.
"UFC is aware that welterweight contender Matt Brown was allegedly attacked today by a former acquaintance at the UFC 198 host hotel in Curitiba, Brazil," the statement said. "UFC has been in communication with local authorities to gather more information relative to the alleged attack, and is reviewing security measures at the hotel.
"Fortunately, Brown was uninjured in the situation and will return home to the United States later today as planned."
A spokesman for the Curitiba Police department confirmed with MMA fighting that Botti had decided to press charges against Brown's friend, believed to be Vinicius Lemos.
Brown's wife Colleen took to Twitter to criticise Botti, labelling him "an absolute psycho", while also reminding people of an incident last year when the pair were involved in an altercation.
While the antics surrounding Brown drew plenty of attention during the fight night, Stipe Miocic also got people talking with an impressive knockout win over Fabricio Werdum to claim the heavyweight championship.
Werdum chased the American around the Octagon as he looked to take control of the fight but was floored by a counter right hand, which Miocic threw without even setting his feet.
"He's quicker than I thought so he was catching me off guard and forcing me to go backwards," Miocic said.
"But I practice going backwards all the time. I've got power."
Miocic followed up the punch with a couple of finishing blows on the ground before the referee intervened. He immediately jumped out of the Octagon to embrace his team and cried: "I'm the world champ."
Werdum hadn't fought for 11 months after injuries delayed his defence of the title he won against Cain Velasquez last year. He vowed to return.
"He was better than I was tonight," Werdum said. "But I'm going to come back here and I'm going to be the champion."
-News.com.au