'That was scary': Aussie fighter cops sickening KO at UFC 243

The main event of UFC243 in Melbourne began in brutal fashion, with Australian fighter Justin Tafa knocked out by a powerful blow from opponent Yorgan de Castro in the opening round.

Tafa’s American opponent saw his chance to strike as the hometown fighter advanced, leaving his chin wide open.

An absolutely lethal right hand dropped Tafa to the canvas, where he stayed for several minutes as he was assessed by medical staff.

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“Holy smokes, he put him to sleep!” was the call from the commentary booth, while fans on social media were left in awe of the devastating strike.

The knockout continued a nightmare run for the Australian fighters on the card, after fellow Aussie Nadia Kassem was brutally felled in her match against Ji Yeong Kim.

Speaking after the fight, De Castro said he had to take advantage of the opportunity as soon as it presented itself.

"I was expecting three rounds of war, but he came hard at me with his chin open," he said.

Australian fighter Justin Tafa is brutally knocked out by American Yorgan de Castro at UFC 243 in Melbourne. Pictures: Getty Images

"I knew I just had to time him. I have power, man. If I land, they're going down."

Earlier in the card, Australian Jake Matthews took a relatively risk-free points victory over Rosern Akman, while Jamie Mullarkey and Brad Riddell put on a show with a veritable slug-fest.

'Hard to watch': Nadia Kassem outclassed at UFC 243

The local fighters have experienced a mixed start to UFC 243 in Melbourne, with Aussie Nadia Kassem on the receiving end of a brutal loss.

Kassem was beaten by Ji Yeon Kim late in the second round of their flyweight bout at Marvel Stadium on Sunday.

The referee stopped the fight with just one second left in the round after Kassem received a number of brutal punches that left her bleeding from the nose.

“The long finishing sequence was a little hard to watch,” ESPN’s MMA expert Ariel Helwani tweeted.

Kassem was distraught as she left the Octagon - her record now 1-2 with both losses in Australia.