'Absolutely shameful': US Open crowd blasted for booing injured Novak Djokovic

Djokovic's US Open title defence came unstuck on Sunday when a nagging shoulder injury forced the world number one to retire from his fourth-round match against Stan Wawrinka, prompting a chorus of boos from the crowd at Flushing Meadows.

Wawrinka was leading 6-4 7-5 2-1 when Djokovic decided he could not continue, the pair embracing at the side of the court before the Serb walked off with his head down low but his left thumb stuck high in the air.

After dropping the second set, Djokovic immediately called for medical attention and sat courtside without his shirt on while the trainer gave him a massage.

He returned to the court but the 16-times Grand Slam winner was still clearly hampered by the issue and after being broken to love following a double fault decided he could not go on.

Despite clearly playing through the pain, Djokovic was not greeted by a huge amount of sympathy from the crowd inside Arthur Ashe Stadium as boos rang out around the arena.

Twitter exploded in response to those who booed the Serbian, with some describing the culprits as "disgusting".