"I would like to apologize to all my supporters and fans of MMA for not being able to put on the show you deserve," Whittaker wrote on Instagram.
"I've been ruled medically unable to compete and won't be able to defend on home soil. This card meant so much to me and I'm devastated for not being able to fight. All I can do is focus on getting healthy to come back better than ever. All the best to Yoel and Luke for their fight and I'll be waiting."
A post shared by Robert Whittaker (@robwhittakermma) on Jan 13, 2018 at 12:34am PST
The 27-year-old was installed as undisputed champion when Georges St. Pierre vacated the title shortly after defeating Michael Bisping at UFC 217 in November.
The Sydney native was on a eight fight winning streaking, including the decision victory over Romero at UFC 213 on July 8 where he claimed theinterim middleweight belt.
Rockhold, meanwhile has rebounded from his title loss to Bisping at UFC 199 with a second-round stoppage of David Branch at UFC Fight Night 116.
As for Romero he was on an eight-bout winning streak that included triumphs over Chris Weidman, Ronaldo Souza, Lyoto Machida and Derek Brunson before his defeat to Whittaker,.
Romero was originally scheduled to face Branch at UFC on Fox 28 on February 24 and it is still unclear if the former WSOF Middleweight and Light Heavyweight Champion Branch will remain on the Florida card.