The top two seeds, Australia's Ashleigh Barty and Romania's Simona Halep, respectively, scored quarterfinal victories Friday and moved on to the semifinal round at the Porsche Tennis Grand Prix in Stuttgart, Germany.
Fourth seed Elina Svitolina of Ukraine joined them, advancing past seventh-seeded Petra Kvitova of the Czech Republic 6-7 (4), 7-5, 6-2.
Svitolina needed two hours, 37 minutes to win the match, saving 13 of 16 break points (81.3 percent).
The No. 5 seed Aryna Sabalenka of Belarus will meet Halep after winning a three-set marathon in two hours, 28 minutes, 7-5, 4-6, 6-1 over Estonia's Anett Kontaveit.
Halep cruised past Ekaterina Alexandrova of Russia 6-1, 6-4, saving eight of 10 break points while winning 70 percent on her first serve.
Barty struggled to move past the Czech Republic's Karolina Pliskova, winning 2-6, 6-1, 7-5. Pliskova was perfect in break points but had only three such opportunities the entire match.
In the decisive third set with Pliskova serving, Barty won 13 of 18 second-serve points while Pliskova managed to win only five of 15 points off Barty's second serves.
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Top-seeded Elise Mertens of Belgium defeated unseeded Katerina Siniakova of the Czech Republic 6-4, 6-4 to advance to the semifinals where she'll meet third-seeded Veronika Kudermetova of Russia.
Kudermetova took down Ana Bogdan of Romania 2-6, 6-3, 6-3.
The other semifinal features a pair of unseeded players.
Ukraine's Marta Kostyuk beat Ana Konjuh of Croatia 7-5, 4-6, 6-3, while Romania's Sorana Cirstea advanced after winning the first set, 6-4, against France's Fiona Ferro (NYSE:FOE) who had to retire.
(Field Level Media)