Jose Aldo pulled out of his featherweight title defense against Conor McGregor at UFC 189 next weekend.
UFC president Dana White made the news official Tuesday night on SportsCenter.
Chad Mendes will replace Aldo and challenge McGregor for an interim title on July 11 in Las Vegas.
"I expected something, I predicted something would come about," McGregor said Tuesday afternoon at the unveiling of Reebok's new UFC apparel. "I feel he left the world tour emotionally invested. I knew he would hit training hard. I knew the body would shut down and that's what happens. You must be intelligent with your approach to training because 14-15 weeks out from a fight, you cannot slug it out day in day out. the body gives out."
Last week, news reports out of Brazil said Aldo had a broken rib. Several days later, the UFC said doctors deemed it a bruised rib and that he could fight if he wanted.
"I wanted to jump out of the building, but I was on the first floor, so it wasn't going to matter," UFC chairman Lorenzo Fertitta said at the Reebok event when asked about his initial reaction to Aldo's possible rib injury.
"I took a knee, man," UFC president Dana White said about that day last week. "I took a knee. We literally were in the board room, I'm laying in my chair."
Aldo vs. McGregor was on track to be the biggest fight of the year, both in terms of projected ticket gate and pay-per-view buys. White said earlier Tuesday that the UFC had spent $10 million promoting and marketing Aldo vs. McGregor.
"If there's one fight you didn't want to fall out, it would be this one," White said. "But you can't control it. You can't let it kill you."
At Tuesday's Reebok event, White sounded confident that Aldo would fight McGregor.
But on Tuesday evening, Aldo's coach Andre Pederneiras called UFC officials to say Aldo couldn't fight.
"It's part of what we have to manage on a show-to-show basis," Fertitta said. "At the end of day, it's his call, his decision. We made that very very clear. That's why we put in the backup plan."