It marks the second time Whittaker has been forced to withdraw from a scheduled title fight in Australia.
In the co-main event Israel Adesanya looks to collect even more hype by finishing Anderson "The Spider" Silva.
Kelvin Gastelum is trying to put a positive spin on losing his chance to fight for the middleweight title at UFC 234. "His injury isn't believed to be related to his weight cut".
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The UFC will stage its first pay-per-view of 2019 from Australia, and fight fans at the Rod Laver Arena in Melbourne - home of the Australian Open - will see two massive middleweight matchups.
Earlier this week, White had said the winners of the Whittaker-Gastelum and Adesanya-Silva fights would meet later this year.
ESPN first reported the news and said Whittaker's withdrawal was not a result of weight cutting issues. The Brazilian will take on a fighter 14 years his junior in Adesanya, who is sixth in the UFC middleweight rankings and 15-0 in his MMA career.
The Sydney-based star has experienced a horror run of injuries and illness throughout his career, including a gruesome abscess infection which forced him to pull out of UFC 221 in 2018.