Seven-time champion Serena Williams is out of the Australian Open, going down in a thriller to seventh seed Czech Karolina Pliskova, who saved four match points on her way to victory.

A visibly emotional Williams left the court within just a minute of her shock loss on Wednesday.

She had earlier stormed back to level the score at a set apiece after Pliskova won the first set. Then the American champ stormed away to a 5-1 final-set lead.

Pliskova’s spirited comeback was sparked when facing the first of the match points.

Williams was called for a foot fault on her first serve, before Williams appeared to jar her ankle while changing direction.

While the ankle looked to visibly trouble Williams, she had three further chances to close out the match at 5-4, but her opponent’s improved aggression saw those opportunities come and go.

I don't know that I've ever seen a match with a match point twist like this. Holy wow. #AusOpen

— Ben Rothenberg (@BenRothenberg) January 23, 2019

Rarely have we seen Serena Williams collapse (out of gas/tweaked ankle) that close to the finish line in a major quarterfinal.

Up 5-1 on Pliskova in the third set and with four match points on her serve. Meek bow-out, barely chasing balls in final two games.

Shocking. #AusOpen

— Richie Whitt (@richiewhitt) January 23, 2019

Pliskova, who previously made the 2016 US Open final and was looking to avenge last year’s quarter-final loss to Williams in New York, reeled off six straight games to eventually run away with the unlikely victory.

In her post-match interview, Pliskova said that while the momentum was firmly on Williams’ side, she retained a faint glimmer of hope in the final set.

“I was almost in the locker-room but now I am standing here as a winner – it is a very good feeling,” she said after the two-hour 10-minute tussle.

Karolina Pliskova rode a wave of momentum in the closing stages of the final set to reach the last four. Photo: Getty

Williams, 37, remains one grand slam title shy of tying Margaret Court’s all-time record of 24 major singles titles, having also lost to Japan’s Naomi Osaka in controversial circumstances in last year’s US Open final.

Pliskova will face Osaka at Rod Laver Arena on Thursday, with the winner to progress to Saturday night’s final.

US Open champ powers on

Reigning US Open champion Osaka became the first Japanese woman in 25 years to reach the Australian Open semi-finals, following a comprehensive 6-4 6-1 victory over Ukraine’s Elina Svitolina.

The world No.4 had little difficulty dispatching last year’s WTA Finals champion, who sought treatment for a neck injury during the lopsided second set.

Osaka’s biggest threat came in the form of a pesky bee, which chased her around Rod Laver Arena in the dying stages of the match.

Help!@Naomi_Osaka_ is being attacked by a fly on centre court 😬😅#AusOpen pic.twitter.com/BUEFqbrAv7

— #AusOpen (@AustralianOpen) January 23, 2019

The 21-year-old is the first Japanese woman to reach the final four at Melbourne Park since Kimiko Date in 1994.

Osaka said she placed an emphasis on controlling her temperament, following consecutive three-set matches in the past two rounds.

“For me today I just had one goal and that was to try as hard as I can get and not get angry,” Osaka said.

“I didn’t do that well in the last two rounds so that was my only goal and I think I did it well, so I’m really happy with the way I played.

“She is a really great player and it is kind of unfortunate that she got injured but playing against her even when she was injured was still really tough.”