The move contentious a whirlwind 12 months for No. 5 ranked heavyweight, who is also embroiled in an ongoing legal battle with both the UFC and American megastar Brock Lesnar.
Hunt is demanding punitive compensatory damages from both after Lesnar failed two drug tests following their blockbuster encounter at UFC 200.
In his first person article for Players Voice, Hunt wrote: "My body is f ... ed but my mind is still here. I've still got my senses about me and I know what's right and wrong, which is the main thing.
"Sometimes I don't sleep well. You can hear me starting to stutter and slur my words. My memory is not that good anymore.
"I'll forget something I did yesterday but I can remember the shit I did years and years ago. That's just the price I've paid - the price of being a fighter.
"But I've fought a lot of drug cheats and copped a lot of punishment from guys who were cheating and that's not right."
A UFC official said on Wednesday morning: "Following a recent first-person article published by heavyweight Mark Hunt, the UFC has taken the precautionary steps of removing Hunt from a previously announced bout in Sydney, Australia.
"The health-related statements made by Hunt in the article represent the first time UFC was made aware of these claims. "Athlete health and safety is of the utmost importance to the organisation and it would never knowingly schedule an athlete complaining of health issues for a fight. The organisation will require that Hunt undergo further testing and evaluations prior to competing in any future UFC bout."
Despite his ongoing legal action against the UFC, Hunt has already fought twice this year - losing to Alistair Overeem via KO in March before rallying to beat Derrick Lewis, who was on a six-win streak, via TKO in June.
Given his popularity Down Under, the Auckland-born fighter was the obvious choice to headline the Sydney event.
Ironically, Werdum was initially offered to be Hunt's opponent on next month's Fight Night card, but accepted a fight against Derrick Lewis at UFC 216 last Sunday, instead.
Lewis, however, withdrew from the Las Vegas card at the 11th hour because of a back injury.
As a result, Werdum instead was pitted against Alabama native Walt Harris, who was promoted on just three hours notice.
The Brazilian required only 65 seconds to make Harris tap from an armbar.
So now, he heads Down Under.