Simona Halep and Venus Williams were among the casualties on a day of surprises in the first round of the Australian Open, but Victoria Azarenka was in ominous form on Tuesday.
Halep, who is yet to win a grand slam, put in a disjointed performance as she was beaten 6-4 6-3 by an emotional Zhang Shuai, while Williams (8) was defeated by Australia-born Briton Johanna Konta 6-4 6-2.
It was a better day for Garbine Muguruza, though, the third seed routed Anett Kontaveit 6-0 6-4.
And it was even easier for two-time champion Victoria Azarenka, fancied by many to triumph in Melbourne, as the 14th seed raced to a double-bagel win over Alison Van Uytvanck.
Romanian Halep had reached the quarter-finals in Melbourne for the past two years, but an Achilles injury has plagued her in the 2016 build-up to the tournament.
Halep fought back from 4-0 down in the first set to trail 5-4 before being broken to lose and then led 3-1 in the second, but gave up her serve twice in the last four games to bow out.
Williams, a 2003 finalist in Melbourne, enjoyed a renaissance of sorts in 2015 by returning to the top 10. The 35-year-old American, a seven-time grand slam winner, had limited match time in the build-up to the tournament and that possibly contributed to her sluggish showing against Konta.
Muguruza reached the final of Wimbledon last year and was clinical versus Kontaveit, while Azarenka was on court for just 53 minutes in a devastating display.
SEEDS SAYING GOODBYE
After seven seeds tumbled on day one a further five fell on Tuesday with Halep and Williams the biggest casualties.
Irina-Camelia Begu (29) was defeated 6-3 6-2 by Johanna Larsson, while Lesia Tsurenko (31) and Caroline Garcia (32) also bade farewell to Melbourne for another year having lost to Varvara Lepchenko and Barbora Strycova respectively.
Zhang had previously never won a match in a grand slam and held a 0-14 record at major tournaments before upsetting Halep.
Azarenka became just the eighth woman to record a double bagel at the Australian Open and has now achieved the feat at every major.
Zhang became the fourth Chinese woman to reach round two this year, the most from the nation since 2006.
Halep became the first top-two seed to lose in the Australian Open first round since 1979.
SOCIAL MEDIA SWEEP
"Such an awesome experience on Rod Laver! Thanks for the support!" - Australia-born Konta laps up her victory over Williams.
"Take a bow @JoKonta91." She had plenty of support from two-time grand slam champion Andy Murray.
"Shuai Zhang is making me all teary eyed being all emotional after her win over Halep. Her first grand slam win in 15 attempts." - Heather Watson on her delight at Zhang's upset of Halep.
THEY SAID WHAT?
"Before when I had this feeling, everybody said 'no come on, you're a great player you can come back soon. You have to keep going.'" - Zhang reveals that past struggles made her consider retirement.
"I'm pretty pleased with my level, and obviously that I was really concentrated during the whole match." - Muguruza feels in good shape after her fine start.
"I think I let her play her best tennis. I didn't hit very strong and I didn't hit with good strength." - Halep rues her off-colour performance.
"If I would have left for a man I'm sure that would have been illegal and the police would be involved, I can assure everybody that I did not elope at the age of 11. We wanted to move. I'm lucky to call myself British." - Konta, somewhat tongue-in-cheek, denies she left Australia for the UK because of a man.
Azarenka can look forward to a second-round tie with Danka Kovinic on Thursday, while Konta and Zhang face Zheng Saisai and Alize Cornet following their shock wins.
On Wednesday, world number one and defending champion Serena Williams is back in action against Su-wei Hsieh and last year's runner-up Maria Sharapova plays Aliaksandra Sasnovich.
Zhang Shuai beat Simona Halep (2) 6-4 6-3
Garbine Muguruza (3) beat Anett Kontaveit 6-0 6-4
Angelique Kerber (7) beat Misaki Doi 6-7 (4-7) 7-6 (8-6) 6-3
Johanna Konta beat Venus Williams (8) 6-4 6-2
Karolina Pliskova (9) beat Kimberly Birrell 6-4 6-4
Timea Bacsinszky (11) beat Katerina Siniakova 6-3 7-5
Victoria Azarenka (14) beat Alison Van Uytvanck 6-0 6-0
Madison Keys (15) beat Zarina Diyas 7-6 (7-5) 6-1
Elina Svitolina (18) beat Victoria Duval 6-2 6-3
Jelena Jankovic (19) beat Polona Hercog 6-3 6-3
Ana Ivanovic (20) beat Tammi Patterson 6-2 6-3
Ekaterina Makarova (21) beat Maddison Inglis 6-3 6-0
Johanna Larsson beat Irina-Camelia Begu (29) 6-3 6-2
Sabine Lisicki (30) beat Petra Cetkovska 6-4 6-4
Varvara Lepchenko beat Lesia Tsurenko (31) 6-7 (5-7) 6-2 6-3
Barbora Strycova beat Caroline Garcia (32) 6-2 6-4
Yaroslava Shvedova beat Tsvetana Pironkova 6-4 6-4
Vania King beat Mona Barthel 3-6 7-5 6-4
Tatjana Maria beat Olga Govortsova 6-4 6-3
Kirsten Flipkens beat Mirjana Lucic-Baroni 5-7 6-2 7-5
Julia Goerges beat Andreea Mitu 6-3 6-4
Laura Siegemund beat Kiki Bertens 6-4 7-5
Annika Beck beat Priscilla Hon 6-0 6-3
Anastasija Sevastova beat Jarmila Wolfe 6-0 4-2 (retired)
Naomi Osaka beat Donna Vekic 6-3 6-2
Alexandra Dulgheru beat Storm Sanders 6-4 6-2
Saisai Zheng beat Carina Witthoeft 6-1 6-2
Lara Arruabarrena beat Maryna Zanevska 6-7 (4-7) 6-3 6-3
Danka Kovinic beat Samantha Crawford 6-2 6-4
Denisa Allertova beat Bethanie Mattek-Sands 6-4 6-7 (5-7) 6-3
Alize Cornet beat Bojana Jovanovski 6-1 6-0
Madison Brengle beat Coco Vandeweghe 6-3 6-4