Australia's Samantha Stosur wasted a match point before crumbling to a three-set loss to Simona Halep in the fourth round of the Miami Open.
Stosur broke the Romanian third-seed twice to win the first set before charging to within a point of an upset victory with a 5-3 lead in the second.
But the world No.5 rallied to take the next seven games before running away a 4-6 7-5 6-2 winner on Monday (Tuesday AEDT).
Halep will meet Johanna Konta in the quarter-finals after the Briton steamrolled Spain's Lara Arruabarrena 7-5 6-1.
It was world No.19 Stosur's best WTA tournament performance this year after bettering third-round efforts in Doha and Taipei.
Top seeds Angelique Kerber and Karolina Pliskova reached the quarter-finals while French Open champion Garbine Muguruza retired from her match with Caroline Wozniacki after dropping the first set.
German Kerber, the top seed, cruised by Japanese qualifier Risa Ozaki 6-2 6-2 while Czech second seed Pliskova beat 15th-seeded compatriot Barbora Strycova 6-1 6-4.
Kerber was barely tested in her 62-minute match during which she displayed a great arsenal of shots and was all over her opponents' serve.
Pliskova cruised through her first set in 22 minutes and looked ready to wrap up a quick victory when she went ahead 5-2 in the second but Strycova found life late in the match breaking Pliskova then holding at love.
"Everything was fine, going well, until 6-1, 5-2," Pliskova, who fought off three break points in the final game, said in a report on the WTA website.
"I was happy to close it because the end was tricky - the end was a little bit shaky."
Sixth seed Muguruza took a medical time-out after dropping the first set 7-6 (7-1) to Wozniacki after feeling dizzy and decided she was unable to continue against the Dane.
"I started normal, and then like at 3-3 or something like this I started to feel headache, pain in my stomach," Muguruza said. "And then it kind of went more and more during the match.
"When I was getting to the 5-4, something like this, I started to feel a little bit dizzy. I think it was the heat? The heat affected me suddenly like that."
With the win, Wozniacki advanced to sixth quarter-final in seven 2017 events.
In other women's action, former Czech world No.5 Lucie Safarova beat Slovakian fourth seed Dominika Cibulkova 7-6 (7-5) 6-1 to reach the last eight.
For unseeded Safarova, who is on the comeback trail from a bacterial infection that hampered her for parts of the past two seasons, the win marked her first top-10 victory since 2015.
