Denis Kudla overcame third seed Jack Sock in straight sets in Atlanta to reach his third ATP World Tour quarter-final.
Rafael Nadal looked closer to his potent best as he beat Jiri Vesely to reach the quarter-finals of the Hamburg Open.
Annika Beck, Teliana Pereira and Bethanie Mattek-Sands all booked their spots in the semi-finals of the Brasil Tennis Cup.
Joao Sousa survived three match points against Denis Istomin to book his place in the quarter-finals of the Swiss Open.
Roger Federer has withdrawn from next month's Rogers Cup in Montreal as he ramps up his preparation for the US Open.
Top seed Tatjana Maria crashed out of the Brasil Tennis Cup in straight sets on a day when three seeds fell.
Second seed Vasek Pospisil battled to a second-round victory over Yen-Hsun Lu at the BB&T Atlanta Open on Wednesday.
Feliciano Lopez fought back to defeat Julian Reister and seal his place in the quarter-finals of the Swiss Open.
British No 2 Aljaz Bedene reached the quarter-finals of the Hamburg Open after knocking out Roberto Bautista Agut.
Steve Johnson was given a work out as he made it through to the second round of the BB&T Atlanta Open on Tuesday.