Naomi Osaka

The world No 1 has struggled since collecting her second grand slam title at the Australian Open this year. She has been plagued by fitness concerns, endured an early defeat at the French Open and struggled to put her disappointment into words after losing in the first round at Wimbledon, since when things have not got much better. A knee injury forced her to quit against Sofia Kenin in Cincinnati and has placed her defence of the US Open title in serious doubt.

Ashleigh Barty

The Australian’s stint at the top of the rankings ended this month and she blew a chance to regain the No 1 spot when she lost her Cincinnati semi-final to Svetlana Kuznetsova. There was also a surprise defeat by Kenin at the Canadian Open amid a growing sense that Barty is finding it hard to live up to the hype after winning the French Open, with a fourth-round defeat at Wimbledon an unexpected setback. She will hope to assert herself in New York.

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Karolina Pliskova

The Czech’s big serve and powerful groundstrokes can blow her opponents to smithereens on hard courts and she has a decent pedigree at the US Open, where she was a beaten finalist in 2016. Yet there remains a sense that Pliskova could show us so much more. Her ranking rarely dips but she is yet to win a grand slam title and she heads to Flushing Meadows a little bruised after quarter-final defeats against Bianca Andreescu in the Rogers Cup and Kuznetsova in Cincinnati.

Simona Halep

When she is on her game few can live with the punchy Romanian, who proved she is no one-slam wonder when she collected her second major title with a brilliant victory over Serena Williams in the Wimbledon final. The likable 27-year-old gathered awesome momentum as she rolled through the draw at SW19 and Williams was no match for her. The question now is whether Halep, who looked weary in Cincinnati, can find another burst of energy in New York.

Serena Williams

A solid run of matches remains out of reach for Williams, who lost last year’s final to Osaka in unforgettable circumstances. At Wimbledon she paid for her lack of sharpness when a string of easy wins over moderate opponents proved no way to prepare for Halep’s athleticism and there was more frustration when back spasms forced her to retire after four games of her Rogers Cup final against Andreescu. The injury stopped her going to Cincinnati and means she could be rusty at Flushing Meadows.