"I'm beyond disappointed that I'm unable to defend the title in my home country of Australia".
After beating Romero at UFC 213, Whittaker underwent knee surgery and was unable to fight for six months.
While Rockhold vs. Romero is a high-quality replacement for Whittaker vs. Rockhold, it is likely to disappoint fans in Perth and those who had planned to travel from other parts of Australia.
Whittaker became the interim champion with a win over Yoel Romero at UFC 213 and he was set to make his first official title defense at UFC 221 on February 10, in his home country of Australia but unfortunately, that fight will no longer be happening.
"All I can do is focus on getting healthy to come back better than ever".
Whittaker was installed as the full-time middleweight champion after Georges St-Pierre vacated the belt he won off of Michael Bisping at UFC 217 in November when it was discovered he was battling ulcerative colitis. "All the best to Yoel and Luke for their fight and I'll be waiting..."
A former Cuban Olympic silver-medalist wrestler, Romero was scheduled to face Branch at a UFC Fight Night event on February 24. Romero and Rockhold will compete in a five-round bout with a belt on the line as the promotion is introducing yet another interim title.
Whittaker was an obvious choice to headline the event, as he is the first Australia-based champion in UFC history.
33-year-old Rockhold, meanwhile, defeated Branch via TKO back in September.