Miami - Fourth-seeded Dominika Cibulkova of Slovakia was knocked out of the Miami Open by the Czech Republic's Lucie Safarova on Monday while Spanish sixth seed Garbine Muguruza was also eliminated.
Safarova, ranked 36th in the world, moved into the quarter-finals with a 7-6 (7/5), 6-1 victory -- her first triumph against a top-10 opponent since 2015.
The 30-year-old Czech will face Dane Caroline Wozniacki, who advanced when Muguruza retired from their match due to illness shortly after losing the first set 7-6 (7/1).
In an all-Czech clash, second seed Karolina Pliskova defeated Barbora Strycova 6-1, 6-4.
Later matches Monday feature American Venus Williams against seventh-seeded Russian and Indian Wells runner-up Svetlana Kuznetsova and world number one Angelique Kerber against Japanese qualifier Risa Ozaki.