Birmingham - Japan's 43-year-old Kimiko Date-Krumm has caused a major surprise on Thursday when she knocked out defending Edgbaston grasscourt champion Daniela Hantuchova 6-4, 6-0 on a day of upsets in Birmingham.
Second seed and 2011 US Open champion Sam Stosur of Australia also slumped to a third round defeat against compatriot Casey Dellacqua, who continued her rich vein of form with a 2-6, 6-2, 6-2 victory.
Slovakia's Hantuchova admitted she was well beaten on the day; "Going into the match, I felt very confident and I thought I had those chances early in the beginning of the first set to maybe break her.
"But after that, she just didn't really give me a chance. I tried everything, and I mean, she was hitting lines, moving well, coming to the net, serving unbelievably well.
I thought I was always going to have chances on her serve, but today just everything went her way".
Elsewhere top seeded Ana Ivanovic of Serbia enjoyed an easy day at the office as she lost just two games against American Lauren Davis and advanced easily.
She coasted to a 6-1, 6-1 thrashing to reach the last eight.
Third seed Sloane Stephens had a much tougher time against fellow American Alison Riske but finished strongly to win 7-6 (7/4) 2-6 6-1.
It was a similar story for fourth seed Kirsten Flipkens of Belgium, a semi-finalist at Wimbledon last year, who came from a break down in the second set to defeat Canada's Aleksandra Wozniak 1-6 7-5 6-4.
The world number 25 now faces Barbora Zahlavova Stycova of the Czech Republic for a place in the last four.
Finally, fellow Czech Klara Koukalova reached the quarter-finals along with ninth seed Zhang Shuai of China.
Collated results from the fourth day of the WTA Birmingham Open on Thursday (x denotes seeding):
Ana Ivanovic (SRB x1) bt Lauren Davis (USA) 6-1, 6-1
Klara Zakopalova (CZE x6) bt Coco Vandeweghe (USA) 3-6, 7-6 (7/3), 6-4
Sloane Stephens (USA x3) bt Alison Riske (USA x15) 7-6 (7/4), 2-6, 6-1
Barbora Zhlavov Strcov (CZE) bt Tmea Babos (HUN) 6-2, 0-6, 6-3
Zhang Shuai (CHN x9) bt Petra Cetkovsk (CZE) 6-0, 7-6 (8/6)
Kimiko Date Krumm (JPN) bt Daniela Hantuchova (SVK x7) 6-4, 6-0
Casey Dellacqua (AUS x16) bt Samantha Stosur (AUS x2) 2-6, 6-2, 6-2
Kirsten Flipkens (BEL x4) bt Aleksandra Wozniak (CAN) 1-6, 7-5, 6-4