Kelvin Gastelum is disappointed by the news of Robert Whittaker dropping out of UFC 234 due to a hernia and declares himself the new middleweight champion. (1:28)

Gastelum is devastated by Whittaker dropping out of UFC 234 (1:28)

Kelvin Gastelum, with a title belt draped over his shoulder, called himself "the champ" when speaking with media at UFC 234 on Sunday in Melbourne, Australia.

Gastelum was set to face UFC middleweight champion Robert Whittaker in the card's main event Sunday. Whittaker was forced to pull out of the bout Saturday due to emergency surgery on his bowel and abdomen.

"This is my belt. I earned this," Gastelum said. "I showed up, traveled thousands and thousands of miles from home, made the weight. In my world, the wrestling world, if the guy shows up and makes the weight, for some reason cancels the bout, the guy forfeits the match -- I win. I am the champion."

UFC president Dana White said Whittaker's injury was unexpected and occurred the previous night.

"This was a freak, freak injury," White told ESPN. "It's one of those situations where if it had popped out during the fight it could have been fatal for him."

Gastelum is coming off wins against Ronaldo "Jacare" Souza and Michael Bisping. Whittaker, according to White, is expected to miss four to eight weeks. He is on a nine-fight winning streak.

Whittaker's management team posted on social media that the fighter will remain hospitalized for several days after undergoing surgery for a "twisted and collapsed bowel" and an "internal hernia of the intestine."

"Hopefully Rob heals up great," Gastelum said, "I wish him a speedy recovery and when he heals up maybe he can get a crack at my title."