• Stan Wawrinka was leading match 6-4, 7-5, 2-1
  
• Serbian world No 1 suffering with shoulder complaint
  

Novak Djokovic’s US Open title defence came to a halt on Sunday when the Serb retired from his fourth-round match against Stan Wawrinka due to a shoulder injury.

Wawrinka was leading 6-4, 7-5, 2-1 when world No 1 Djokovic, who won four of the last five grand slam titles, decided he could not continue and walked off the Arthur Ashe Stadium court to a chorus of boos.