It means the no less anticipated co-main event between Israel "The Last Stylebender" Adesanya and Brazilian legend Anderson Silva will top proceedings Down Under.
Per Okamoto, the hernia was not related to Whittaker's weight cut.
Evidently, Whittaker began complaining of pain in his abdomen during the middle of the night and was taken to the hospital.
The UFC is back in Australia for today's UFC 234 event.
Silva was guaranteed a title shot by White if he defeats Adesanya at UFC 234 at Rod Laver Arena in Melbourne this weekend.
Whittaker was set to defend his title for the first time since becoming interim champion at UFC 213.
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.
Injuries kept him from fighting Luke Rockhold at UFC 221 in Perth a year ago.
He is a heavy favorite going up against the 43-year old Silva, who has not fought in two years, and a victory should catapult the entertaining Style Bender into the main event scene.