Yulia Putintseva claimed a second straight victory over Naomi Osaka to dump the second seed out of Wimbledon on the opening day.
Osaka's last match before arriving at the All England Club was a straight-sets loss to Putintseva at the Nature Valley Classic in Birmingham and again the Kazakh proved too consistent.
Osaka led by an early break but could not hold onto her advantage and Putintseva celebrated a 7-6 (4) 6-2 victory and one of the biggest successes of her career.
Osaka bizarrely sat on the grass instead of her chair during changes of ends in Birmingham, saying on Saturday she felt she just needed to try something different.
She looked in a much better place mentally here, striking the ball sweetly and coming to the net regularly, and quickly moved into a 3-1 lead.
But Putintseva is known as one of the best competitors on tour and, after she fought back to level at 3-3, things became increasingly complicated for Osaka.
The Japanese player was the one applying most of the pressure but she could not break and a wild end to the tie-break left her a set down.
It is easy to forget how relatively inexperienced Osaka is such has been the speed of her rise and the poise with which she won her two grand-slam titles at the US Open last summer and the Australian Open in January.
She admitted becoming world number one was hard to handle and she has not won a title since her dramatic victory over Petra Kvitova in the final in Australia.
The 21-year-old also does not feel comfortable on grass despite the surface appearing favourable to her powerful game.
Osaka continued to hit eye-catching winners, particularly off her backhand, but too often Putintseva retrieved one ball more than her opponent was expecting.
The Kazakh benefited from a crucial slice of luck at 2-2 and break point when a mis-hit backhand was shown just to have caught the edge of the line for a winner.
Osaka turned away in frustration while Putintseva fist-pumped her way back to her chair.
Osaka had a chance to break straight back but placed a straight-forward volley wide, and that proved to be the beginning of the end.
When Osaka dumped a final backhand into the net for a 37th unforced error, Putintseva pumped her fist and then looked around Centre Court in disbelief.
