Roger Federer has withdrawn from next month's Rogers Cup in Montreal as he ramps up his preparation for the US Open.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.
Rafael Nadal hit back from a set down to beat fellow Spaniard Fernando Verdasco in Hamburg.
Thomaz Bellucci enjoyed a straight-sets win over Kimmer Coppejans to reach round two of the Swiss Open in Gstaad.
Bethanie Mattek-Sands battled back from deep trouble to advance at the Brasil Tennis Cup in Florianopolis.
Fourth seed Kurumi Nara fell at the first hurdle of the Baku Cup following a straight-sets defeat to Olga Savchuk.