Venus Williams is through to third round of the Family Circle Cup after a battling victory over Chanelle Scheepers in Charleston.
Sister Serena suffered a shock exit to Jana Cepelova on Tuesday but 11th seed Venus had no such trouble as she overcame her South African opponent 7-5 7-5.
Home-favourite Sloane Stephens made a shock exit as she was beaten by Elina Svitolina. The fifth seed never really got going and fell to a 6-4 6-4 defeat.
Another up and coming American also saw her bid ended early as 15th seed Madison Keys lost 6-1 6-7 (7/3) 6-7 (7/4) to Shuai Peng.
There was better news for the other top seeds in action as Sara Errani and Sabine Lisicki both advanced to the third round.
The Italian third seed had taken the first set 6-3 against Kiki Bertens when her opponent retired while fourth seed Lisicki beat Vania King 7-5 4-6 6-3.
Daniela Hantuchova moved through with a 6-2 6-3 win over Grace Min, Elena Vesnina beat Petra Cetkovska 3-6 6-2 6-4 and Andrea Petkovic was a 6-0 6-0 winner over Lourdes Dominguez Lino in just 49 minutes.
Qualifier Belinda Bencic beat Marina Erakovic 6-2 6-1 while Ajla Tomljanovic beat Shuai Zhang 4-6 7-6 (7/4) 6-3.