Anderson Silva against Israel Adesanya has been moved up to the main event.
Kelvin Gastelum was expected to challenge Robert Whittaker for the promotions middleweight championship in the headliner of tonight's UFC 234 event in Australia.
It is understood a devastated Whittaker will undergo surgery on Sunday. "It wasn't a weight-cutting related issue or anything like that, it's just a very unfortunate hernia issue which may even require a procedure".
Whittaker, who successfully weighed in on Friday, was experiencing pain in his abdomen late last evening and was immediately taken to the hospital where he was diagnosed.
Silva, 43, broke into tears during the UFC 234 official weigh-in.
Whittaker was set to defend his title for the first time since becoming interim champion at UFC 213.
The Octagon returns to the Land Down Under on Saturday night as UFC 234 is live from the Rod Laver Arena in Melbourne, Victoria, Australia. Lando Vannata and Marcos Mariano's lightweight matchup will also be elevated to co-main status.
Earlier this week, White had said the winners of the Whittaker-Gastelum and Adesanya-Silva fights would meet later this year.
Adesanya, a New Zealander who UFC called its breakout star of 2018 in its release, made his UFC debut only a year ago in the preliminary card of UFC 221, the same event that Whittaker had to pull out of.