World number one Caroline Wozniacki crashed out at Wimbledon as Dominika Cibulkova triumphed in three sets to make the quarter-finals.
Wozniacki, 20, is still hunting a Grand Slam trophy and flew through the first set, but was taken to a decider after losing the tie-break in the second.
And Slovakia's 24th seed broke in the 11th game and held serve to shock the Dane and win 1-6 7-6 (7-5) 7-5.
Cibulkova will face 2004 champion Maria Sharapova, who beat Shuai Peng 6-4 6-2.
Fourth seed Victoria Azarenka, 22 in July, eased through her match, beating Russian Nadia Petrova in 64 minutes and will next play Austrian Tamira Paszek, winner over Russian Ksenia Pervak in three sets 6-2 2-6 6-3.
German Sabine Lisicki came through a tight opening set to finally see off Petra Cetkovska 7-6 (7-3) 6-1. She plays France's Marion Bartoli who beat defending champion Serena Williams.
The other quarter-final sees Petra Kvitova go up against Bulgarian Tsvetana Pironkova. Eighth seed Kvitova brushed Belgium's Yanina Wickmayer 6-0 6-2, while Pironkova defeated Venus Williams 6-2 6-3.
Wozniacki's defeat will be the latest frustration for the sport's top-ranked player as she awaits a maiden Grand Slam title.
She reached the final of last year's US Open but has failed to progress beyond the fourth round at the All England Club in five attempts.
"I did my best and it wasn't good enough," conceded Wozniacki. "It's disappointing because when you're up 2-0 with a break and have a lot of break points that you don't convert, that's kind of your own fault."
However, it was a stunning result for former French Open sem-finalist Cibulkova, 22, who enjoyed a surprise victory over highly rated German Julia Goerges to secure her first appearance in the last 16.
On bouncing back from her first-set demolition, Cibulkova said: "I just had to be more aggressive on return and more confident on my return.
"It was a great win because it's very hard to beat her. She's a very defensive player and you have to go for your shots. I was really risking it, my forehand was really working and I went for it."
Wozniacki took only 24 minutes to breeze through the first set and despite being taken to a decider looked set to progress with a 2-0 lead.
And having survived three break points to level at 5-5, it seemed the momentum was back with the Dane, but Cibulkova was relentless and secured her triumph on her third match point.
The Slovakian's reward is a battle with fifth seed Sharapova for a spot in a Wimbledon semi-final.
It was the first time Russian Sharapova had played Peng, seeded 20th, on grass and both struggled with their serves and range early on with error-strewn games.
It went with serve until the ninth game when a double-fault by Peng set the tone and she was broken to 30 with the Russian serving for the set and winning the game to love with some blistering ground strokes.
It was much easier for Sharapova in the second set and she wrapped up the match in one hour 21 minutes, with her fiance, the 6ft 7in New Jersey Nets shooting guard Sasha Vujacic, a vocal supporter.