Karolina Pliskova of the Czech Republic reached her sixth semifinal of the season by defeating Madison Brengle of the United States 6-4, 6-4 at the Generali Ladies on Friday.
The seventh-seeded Pliskova, who is ranked 30th, will next play Anna-Lena Friedsam of Germany, while Camila Giorgi takes on Karin Knapp in an all-Italian semifinal.
Pliskova played four finals this year and won one of them - in Seoul last month. It was the first quarterfinal for the 96th-ranked Brengle, who had a bye in the second round after Ana Ivanovic pulled out injured.
Pliskova converted her only break point at 5-4 to take the opening set and came back from a break down twice to win the second.
Earlier, Friedsam rallied to defeat Stefanie Voegele of Switzerland 4-6, 6-2, 6-3 to advance to her first career semifinal.
The 94th-ranked Friedsam, who won three qualifying matches and beat the third-seeded Dominika Cibulkova in the first round, came back from a break down in the third set and served two aces in the final game.
Giorgi defeated Marina Erakovic of New Zealand 6-3, 7-5. The 42nd-ranked Italian dominated the opening set and recovered from losing three straight games early in the second to reach her third semifinal of the season.
The 59th-ranked Knapp defeated Tsvetana Pironkova of Bulgaria 6-4, 4-6, 6-4 to reach her first semifinal since winning her maiden title in Tashkent last month.
Knapp overcame eight double-faults against the 44th-ranked Pironkova, who had beaten the Italian in straight sets at the U.S. Open.
Knapp failed to serve out the match at 5-3 and missed five match points in the next game before closing out the win.