Aussie Champion Robert Whittaker Pulls The Pin On UFC Title Defence

Aussie UFC champion Robert Whittaker has been forced to abandon his title defence because of a hernia problem.

The middleweight had hoped a raucous home crowd in Melbourne would help him keep his world title against former bounty hunter American Kelvin Gastelum in the Octagon on Sunday.

However  plans for Whittaker's first official title defence were thrown into disarray late Saturday night when the 29-year-old complained of abdominal pain before being diagnosed with a hernia in hospital.

The match between rising New Zealand sensation Israel Adesanya (15-0) and Brazilian legend Anderson Silva (34-8, 1nc) will now serve as the main event.

The wildly popular UFC 234 card sold out in just eight minutes.

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Aussie middleweight champion Robert Whittaker. Image: AAP

Whittaker (20-4) is on a nine-fight winning streak and hasn't lost in five years although he was on the comeback after breaking his hand in his epic showdown with Yoel Romero last June.

Gastelum (15-3 plus one no contest) had predicted the fight would finish in a first round knock-out.

"He might -- a lot of people have said that," Whittaker said in Melbourne on Friday.