Camila Giorgi charged into the Citi Open semifinals as Hsieh Su-wei became the final seed to fall on Friday.
Giorgi has put together a fine run in Washington and the Italian brushed past Zarina Diyas 6-3 6-2 in their quarterfinal at the WTA International event.
The 27-year-old is into her first semifinal of the year after needing just 72 minutes to dispose of Diyas.
Awaiting Giorgi in the last four is American wildcard Caty McNally, who upset fourth seed Hsieh.
Hsieh, the last seed standing at the tournament, was well beaten by the 17-year-old, who claimed a 6-4 6-3 victory.
The other semifinal will be between qualifier Anna Kalinskaya and Jessica Pegula.
Kalinskaya overcame Kristina Mladenovic 6-4 4-6 6-2 and Pegula edged Lauren Davis 6-2 7-6 (7-2).
Sakkari saves four Match Points, stuns Svitolina in San Jose
Elina Svitolina was stunned by a Maria Sakkari comeback in the Silicon Valley Classic quarterfinals, while Aryna Sabalenka moved through on Friday.
Sakkari upset top seed Svitolina 1-6 7-6 (7-3) 6-3 at the WTA Premier event, saving four match points in San Jose.
The Greek seventh seed was trailing 5-2 in the second set before rallying for an incredible victory.
Sakkari will next face Zheng Saisai, who upset 17-year-old fourth seed Amanda Anisimova 5-7 7-5 6-4.
Zheng converted nine of 11 break points, including three from three in the final set, to battle through in two hours, 52 minutes.
Sabalenka and Donna Vekic, the second and fifth seeds respectively, moved into a semifinal clash.
While Vekic was too strong for qualifier Kristie Ahn 7-5 6-0, Sabalenka edged sixth seed Carla Suarez Navarro 3-6 6-2 6-4.