The newly-crowned middleweight champion was supposed to make the first defence of his 185lbs crown at the promotion's second pay-per-view card of the year, which takes place in Australia on February 11. The bout was going to headline UFC 221 inside Perth Arena in Perth, Western Australia.
St-Pierre's move allowed Whittaker to exchange his interim title for the undisputed crown, and news of the fight with Rockhold signaled a return to business for a division that had been slowed by chaos for the past year.
Whittaker, born in New Zealand but raised in Australia, was scheduled to face Luke Rockhold in the main event of UFC 221 in Perth on February 11 but he suffered several significant injuries in training.
"I'm beyond disappointed that I'm unable to defend the title in my home country of Australia". The new main event at UFC 221 will still have championship gold resting in the balance as Rockhold vs. Romero will fight for an interim strap with the victor facing Whittaker in a unification bout later in 2018.
In the long term, UFC 221 had the potential to be a promotional ideal storm similar to UFC Dublin, which cemented Conor McGregor as one of the UFC's top stars.
"I would like to apologise to all my supporters and fans of MMA for not being able to put on the show you deserve", Whittaker wrote on his Instagram account. Romero has been out of action since his loss to Whittaker.
In the short term, despite being well-tailored to the local audience, UFC 221 was a one-fight card for the rest of the world. "All the best to Yoel and Luke for their fight and ill be waiting..."
Rockhold was also the final Strikeforce Middleweight Champion, defeating Ronaldo Souza by decision to win the belt in 2011.
Rockhold will be looking to reclaim the championship he lost by first-round knockout to Michael Bisping at UFC 199 in June 2016.