Stan Wawrinka needed to win a pair of tie-breaks to beat Karen Khachanov in their round-of-16 match at the St Petersburg Open.
France and Croatia are on course to meet in the Davis Cup final after opening up 2-0 leads over Spain and the United States respectively.
Umpire Mohamed Lahyani left his chair to warn Nick Kyrgios about his apparent lethargy before the Australian advanced in New York.
Roger Federer has not dropped a set yet at the US Open as he proved too good for Frenchman Benoit Paire on Arthur Ashe Stadium.
Andreas Seppi saw off Joao Sousa 7-5 6-4 to earn a meeting with 14th seed Nicolas Jarry at the ATP 250 event.
Top seed Rafael Nadal saw off Frenchman Benoit Paire 6-2 6-3 in Toronto on Wednesday.
Seeds David Goffin and Jack Sock were early casualties at the ATP's Rogers Cup in Toronto, where Milos Raonic led the Canadian charge.
Stan Wawrinka said his early exit in Washington was hard to take, but he took it a whole lot better than the fiery Benoit Paire.
Fernando Verdasco and David Ferrer were victorious in Bastad but Benoit Paire tumbled out in Umag.