Novak Djokovic’s US Open defence is over after he was forced to withdraw during his fourth-round clash with Stan Wawrinka while trailing due to a shoulder injury (Stan Wawrinka 9/1 – US Open outright).

Djokovic needed treatment on his shoulder during his third round win over Denis Kudla and was clearly struggling against the Swiss 23rd seed at Arthur Ashe Stadium.

Wawrinka, the 2016 champion, was leading 6-4 7-5 2-0 when Djokovic decided he could no longer continue, leading to loud boos from the crowd.

“It is very frustrating. Of course it hurts that I had to retire,” said Djokovic.

“Some days the pain has been higher, some days with less intensity. Obviously I was taking different stuff to kill the pain instantly. Sometimes it works, sometimes it doesn’t.

“You just know when you know, when you feel like you’re not able to hit the shot any more.”

Wawrinka will take on fifth seed Daniil Medvedev of Russia in the quarter-finals.

Following Djokovic’s exit, Rafael Nadal is the new favourite with Betfred to take the title at 6/5 and Roger Federer is a 9/4 chance.

In the women’s tournament, Britain’s Johanna Konta is through to the last eight of the US Open for the first time in her career after a comeback win over third seed Karolina Pliskova.

Pliskova was a set and a break up but Konta won five games in a row to take the second set before going on to clinch a 6-7(1-7) 6-3 7-5 victory and set up a quarter-final meeting with fifth seed Elina Svitolina.

Six-time champion Serena Williams claimed a routine 6-3 6-4 win over Petra Martic and will face Qiang Wang in the last eight after the Chinese star pulled off a shock 6-2 6-4 victory over second seed Ashleigh Barty.

Williams is the 13/8 favourite to win the US Open outright and Konta is 14/1.

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