Robbie Whittaker claims career-defining win against Souza

Whittaker: Octagon fear never goes away (1:16)

Australian MMA star Robbie Whittaker sits down with ESPN ahead of his fight in Kansas City, revealing how he manages the fear that comes with competing in one of the world's most brutal sports. (1:16)

Robbie Whittaker has claimed a career-defining victory in the Octagon, defeating Ronaldo Souza with a barrage of punches in the second round to send a jolt through the middleweight division.

Whittaker (19-4) was a big underdog against the Brazilian on the UFC Fight Night undercard at the Sprint Center in Kansas City, Missouri, but the New Zealand-born Australian stunned his rival after a tactical first round, dropping him with a right hand 30 seconds into the second before hitting him with a right high kick and unloading with about 90 seconds left to force the stoppage.

"A lot of people let the hype get in their heads given he's a legend of jiu-jitsu and MMA," Whittaker said after the fight of his underdog status. "At the end of the day, it's not a grappling match. It's not a jiu-jitsu match."

The victory was Whittaker's sixth in succession since moving to 185 pounds, and Brett Okamoto reported that he called out world No. 1 Michael Bisping after the bout; the Englisman pulled out of a scheduled fight in 2015 with an injury.

"Bisping owes me a fight," Whittaker said. "We were supposed to fight all those weeks ago and he's cool doing his own thing, but you owe me a fight."

Whittaker told ESPN exclusively before the fight that he was confident he had enjoyed the right preparation to record his biggest win yet.