Serena Williams knocked out of Australian Open by Karolina Pliskova after holding match points

Serena Williams missed four match points before succumbing to Czech seventh seed Karolina Pliskova in a dramatic Australian Open quarter-final.

American Williams, 37, led 5-1 in the final set but lost the last six games as her bid for a record-equalling 24th Grand Slam singles title ended with a 6-4 4-6 7-5 defeat in Melbourne.

Williams seemed unsettled after turning her ankle on her first match point.

The 26-year-old will meet Japan's Naomi Osaka in Thursday's semi-finals.

Williams' inability to seal victory means a highly anticipated rematch of her controversial US Open final defeat by Osaka must wait.

Like Osaka, Pliskova will be playing in the last four here for the first time.

"I was almost in the locker room but now stand here as the winner," said Pliskova, who reached the US Open final in 2016.

"My mind was in the locker room at 5-1 down but I was still here. I was too passive and mentally down. She got a little bit shaky in the end. I took my chances and I won.

"Naomi Osaka is dangerous but there is nobody more dangerous than Serena."