Camila Giorgi saved four match points to edge Wang Qiang in the Bronx Open semi-finals.
A number of seeds crashed out of the top half of the French Open draw, but Simona Halep, Naomi Osaka and Serena Williams remain in the hunt.
For the second time in as many matches at the French Open, Simona Halep had to get through three sets to advance.
Jelena Ostapenko failed to take two match points and was beaten by lucky loser Kristie Ahn, who is ranked 176 places below the Latvian.
U.S. Open champion Naomi Osaka is trying not to look too far ahead at the year's first grand slam.
US Open champion Naomi Osaka is trying not to look too far ahead at the year's first grand slam.
Top seed Karolina Pliskova cannot qualify for the WTA Finals this week, but is on course to feature in Singapore.
Top seed Zhang Shuai defeated Nao Hibino to set up a quarter-final clash with Zarina Diyas at the Japan Women's Open.
Home favourite Nao Hibino put paid to Eugenie Bouchard's hopes of success in Hiroshima, winning their clash in straight sets.
Despite a straight-sets win over Magda Linette at the US Open, Serena Williams feels she can get better.