Seven-time Australian Open champion Serena Williams has been knocked out at the quarter-final stage by seventh seed and also a former world number one Karolian Pliskova, who made one of the most remarkable of comebacks at the Rod Laver Arena.
Serena, who was gunning for a 23rd Major, wasted a 5-1 lead and four match points in the final set to let the Czech player win 6-4 4-6 7-5 in two hours and 10 minutes.
To enter her second Major final, Pliskova will have to get past Naomi Osaka in the semi-final. The Czech player was also a finalist at the 2016 US Open where she lost to Angelique Kerber.
US Open champion Naomi Osaka stayed on course for a second successive Grand Slam title when she beat Elina Svitolina 6-4, 6-1.
The 21-year-old Japanese start hit 31 winners and took full advantage of weak second serves by the Ukrainian, who had a troublesome shoulder in the second set.
"I tried to be consistent or as consistent as I can be. She's really good but unfortunately she was injured. But playing against her injured was really tough. For me, today, I had one goal - it was to try as hard as I can and not get angry. I didn't do that well in the past two rounds, but I played well today," said Naomi.
Osaka was in complete control of the match against Svitolina. In the first five games, both players held serve, but the final five games of the first set were all breaks with Osaka striking the decisive blow when Svitolina netted a backhand.
The second set was much more straightforward after Osaka got the first break in the second game. Svitolina was 0-3 down when she received treatment but it did not have any effects on the match as Osaka punished her second serves and won 16 of 22 points on it.
The Ukrainian did manage to win a game but after one hour and 12 minutes, an Osaka winner sealed the win.
Not since Kim Clijsters reached the semifinals at Australian Open 2006 had a first-time slam winner gone on to progress as far at their subsequent major. Naomi is also in line to become the first woman since former world number one Jennifer Capriati at Roland Garros 2001 to win her first two majors back-to-back.