Andy Murray needs to 'step up' at the US Open, according to John McEnroe.
Top seed Simona Halep crashed out of the New Haven Open after a three-set loss to Magdalena Rybarikova.
Top seed John Isner booked his place in the third round of the Winston-Salem Open with a straight-sets victory over Bradley Klahn.
Daniel Cox has failed to join Andy Murray in this year's US Open men's singles draw after losing his first-round qualifier in New York on Tuesday.
Great Britain's Andy Murray has been seeded eighth for this year's US Open at Flushing Meadows.
Guillermo Garcia-Lopez recovered from a slow start to reach the third round of the ATP Tour's Winston-Salem Open at Wake Forest University.
Caroline Wozniacki had to survive a scare before reaching the second round of the New Haven Open in Connecticut.
Defending champion Rafa Nadal has been forced to pull out of the US Open because of injury.
Roger Federer clinched his first Masters 1000 title in two years by beating David Ferrer 6-3 1-6 6-2 in the final of the Western & Southern Open in Cincinnati.
World No 1 Serena Williams warmed up for the US Open in fine fashion by claiming the Western & Southern Open in Cincinnati with a 6-4 6-1 win over Ana Ivanovic.
Roger Federer will bid to become only the third player in the Open era to notch 80 tour title victories when he takes on David Ferrer in tonight's Cincinatti Masters final.
David Ferrer breezed into the final of the Cincinnati Masters after a routine 6-3 6-2 victory over Julien Benneteau.