The upset left only three of the top 10 seeds still alive in the year's final Grand Slam - number one Serena Williams, who is seeking the fourth women's calendar-year Grand Slam, second seed Simona Halep and fifth seed Petra Kvitova.
A round-up of tennis matches played on Tuesday.
Serbia's Jelena Jankovic crushed leg-weary Caroline Wozniacki to reach the semi-finals of the WTA Championships while American holder Venus Williams reached the last four on Friday without hitting a ball.
Indian tennis ace Sania Mirza and her Czech Republic partner Barbora Strycova stormed into the quarterfinals of the US Open with a straight sets victory in the women's doubles event on Tuesday.
Improving with age is a euphemism not taken to kindly by some women but it would seem in tennis that quality, these days certainly, comes with experience.
Simona Halep's powers of recovery will be put to the test on day eight of the Australian Open on Monday when the world number one meets Japan's Naomi Osaka in a tricky fourth round clash.
Serena Williams will try to take a step closer to history on Saturday when she plays her third-round match at the US Open.
Rafael Nadal, with his troublesome left wrist improving every day, will be eyeing more progress at the US Open on Friday when he bids for a place in the last 16.
Rafael Nadal extended his astonishing winning run on clay to 42 consecutive sets as he reached the semi-finals of the Barcelona Open with a 6-0, 7-5 victory over Slovakia's Martin Klizan on Friday. The defending champion will face David Goffin on Saturday after the Belgian beat Spaniard Roberto Bautista 6-7(3), 6-2, 6-2.
Top seed Caroline Wozniacki of Denmark moved into the quarter-finals at the Family Circle Cup with a 6-2, 7-5 win over Switzerland's Patty Schnyder on Thursday.
Top seed Caroline Wozniacki breezed into the third round of the Family Circle Cup with a 6-4, 6-1 win over Czech Barbora Zahlavova Strycova on Wednesday.
French federation president Bernard Giudicelli has hit out at the country's male players after their disappointing run at Roland Garros, saying they lacked physical strength and grit.
Karolina Pliskova lost her cool over a line call and bashed a hole into the umpire's chair with her racket after suffering a 3-6, 6-3, 7-5 defeat by Maria Sakkari in the Italian Open second round on Wednesday.
Belgian pair Justine Henin and Kim Clijsters will meet in the semi-finals of the Sony Ericsson Open after both advanced through their quarter-final ties on Wednesday.
IMAGES from the Australian Open matches played at Melbourne Park on Wednesday
Caroline Wozniacki resisted a sizzling baseline display from China's Zheng Jie to reach the semi-finals of the Indian Wells WTA tournament with a hard-fought 6-4, 4-6, 6-1 victory on Wednesday.
Second seed Caroline Wozniacki recovered from a second-set hiccup to move into the quarter-finals of the Indian Wells WTA tournament with a 6-3, 3-6, 6-0 victory over Russian Nadia Petrova on Tuesday.
One year after shaking off a crippling foot injury to claim a stunning US Open victory, Sloane Stephens said her follow-up season felt just as good as the American prepares to play in next week's WTA Finals for the first time.
Naomi Osaka has witnessed a huge change in her career after claiming a maiden Grand Slam title in 2018, but the rising star of women's tennis will not be changing her quirky personality in media appearances that has endeared her to so many.
Defending champion Venus Williams eased into the third round of the Dubai Championships on Tuesday with a 6-2, 6-3 victory over Germany's Sabine Lisicki. Top seed Caroline Wozniacki had to recover from 1-5 and save a set point to defeat Slovak Dominika Cibulkova 6-2, 7-6 while second seed Svetlana Kuznetsova received a walkover when Spain's Anabel Medina Garrigues withdrew with a back injury.
The 27-year-old Romanian beat Sloane Stephens at Roland Garros to win her maiden Grand Slam title in June and will have spent 40 weeks at the top of the rankings by the end of the season.
Russia's Elena Dementieva became the latest high-profile casualty at the Pan Pacific Open when the third seed was upset by Ukraine's Kateryna Bondarenko in the second round on Tuesday.
Former world number ones Venus Williams and Ana Ivanovic endured a humbling start to the season after the top two seeds were dumped out of the Auckland Classic in the first round by unheralded opponents.
The Danish World No 3 ended 2017 with the biggest title of her career in Singapore and returned a day after thrashing Madison Brengle in her season opener to hit 21 winners against eight unforced errors in the 53-minute win over Martic.
Women's tennis's biggest names still remaining at the US Open take centre stage on Sunday with Grand Slam winners Maria Sharapova, Venus Williams, Garbine Muguruza and Petra Kvitova all appearing on Arthur Ashe Stadium.
Belgium's Kim Clijsters reached the US Open final on Saturday after defending champion Serena Williams was defaulted on the final point. Clijsters won the match 6-4 7-5, which ended in controversy when the American was called for a foot-fault on a second serve to go match point down. An angry Williams argued with the lineswoman who reported her for verbal abuse. She will meet Caroline Wozniacki of Denmark, who beat error-prone Belgian Yanina Wickmayer 6-3, 6-3.
Something old and something new distinguish the women's semi-finals at the US Open on Friday when young and seasoned rivalries will determine combatants for the singles crown.
The lanky wild card kissed the Montreal court after completing a rousing 3-6, 6-4, 7-6(4) triumph as the 18-year-old became the youngest player to ever reach the quarter-finals of an ATP Masters 1000 event.
IMAGES from the PNB Paribas Open played at Indian Wells in California on Monday
Spain's Garbine Muguruza successfully defended her Monterrey Open title on Sunday when Victoria Azarenka retired injured from her first WTA singles final in three years.
Sania Mirza and her doubles partner Martina Hingis were ousted from the Rogers Cup after the top seeds suffered a straight sets loss to Caroline Garcia and Katarina Srebotnik in Toronto on Saturday.
Holder Venus Williams completed her circuitous route to the WTA Championships final, beating Serbia's Jelena Jankovic 5-7, 6-3, 6-4 on Saturday to set up yet another showdown with sister Serena. Serena, who will end the year as world number one for the first time since 2002, got past Caroline Wozniacki after the Dane pulled out with a stomach injury when trailing 6-4, 0-1.
Czech Karolina Pliskova stopped upset-maker Varvara Lepchenko in the semi-finals at the Bank of The West Classic in Stanford, California, on Saturday.
Teenager Caroline Wozniacki warmed up for Wimbledon with victory in the Eastbourne International grasscourt tournament on Saturday.
Victoria Azarenka suffered a stunning meltdown and blew three match points against world number one Serena Williams before losing 7-6(5), 3-6, 7-6(1) in the third round of the Madrid Open on Wednesday.
When Kim Clijsters beat Caroline Wozniacki of Denmark 7-5, 6-3 to win the 2009 women's singles title at the US Open, she not only added a second Grand Slam triumph to her 2005 US Open victory but also became a champion mother. A look at some Super mums.
Belgian Kim Clijsters crowned her remarkable comeback by beating 19-year-old Caroline Wozniacki of Denmark 7-5, 6-3 to win the US Open women's title on Sunday.
Belgian Kim Clijsters crowned her remarkable comeback by beating Caroline Wozniacki of Denmark 7-5, 6-3 to win the US Open women's title on Sunday.
German Sabine Lisicki clinched her first WTA title by upsetting fifth-seeded Dane Caroline Wozniacki 6-2, 6-4 in the Family Circle Cup final on Sunday.
Top seed Elena Dementieva reached the semi-finals of the Family Circle Cup on Friday when Dominika Cibulkova retired in the second set because of a left thigh strain. The Russian, who had lost only four games in her two previous matches, was leading 6-4 1-0 in the quarter-final when the seventh-seeded Slovakian retired. Olympic champion Dementieva will next meet Denmark's Caroline Wozniacki, who beat France's Virginie Razzano 6-2 6-0.