A recent purple patch for Kiki Bertens continued on Friday, as she defeated fifth seed Elina Svitolina at the Cincinnati Masters.
Lesia Tsurenko appeared to be in control of her match against Simona Halep in Cincinnati, before the Wimbledon champion asserted herself.
Lesia Tsurenko will take on Simona Halep later on Friday after the French Open champion beat Ashleigh Barty in the third round.
Madison Keys lost the opening set but hit 55 winners to upstage Wimbledon champion and fourth seed Angelique Kerber on Thursday.
Prior to her 6-1 6-0 defeat to Johanna Konta in San Jose, Serena Williams discovered some shocking and emotional news.
The International Tennis Federation's proposals for a new Davis Cup format were passed by a vote in Orlando on Thursday.
Simona Halep was leading 4-3 and 30-15 in the final set against Alja Tomljanovic when rain washed out play on Wednesday.
Following her defeat to Petra Kvitova at the Cincinnati Masters, Serena Williams struck an optimistic tone.
Two-time winner Serena Williams exited the Cincinnati Masters on Tuesday, as Caroline Garcia and Karolina Pliskova advanced.
Serena Williams was back on form at the Cincinnati Masters, but she came off second best in a titanic tussle with Petra Kvitova.