Novak Djokovic’s US Open title defence came to an end after he retired injured while two sets down to Stan Wawrinka.
The crowd on Arthur Ashe were stunned when the world number one approached Wawrinka and embraced him while trailing 6-4, 7-5, 2-1.
Djokovic has been bothered by a left shoulder injury all week, although it was not apparent during the opening two sets with Wawrinka reprising the sort of form which made him the champion in 2016.
But the Serbian took a medical time-out after dropping the second set, and three games into the third he decided enough was enough.
It means Wawrinka will face fifth seed Daniil Medvedev in the quarter-finals, while the draw has opened up for Roger Federer, who was in imperious form against David Goffin and had been expected to run into Djokovic in the last four.
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After deciding to call it a day, the spectators in attendance were less than impressed with the Serbian, and actually chose to boo him off the court.
Despite the hostile reception, Djokovic waved to the crowd, but the boos rang out as the fans let him know what they thought.
Commentators were surprised by the reaction, and claimed he didn't deserve to be booed, something that Wawrinka agreed with after the match.
The Swiss star said afterwards: "Always surprised when you play the No. 1 and you hear the fans booing him when he had to retire, that's for sure. Again, he's a good friend. I know him really well.
"He's an amazing champion, and if he has to retire, it's not the best for a tennis player to have to leave the court like that."
Although the reaction from the crowd may have been unfair, Djokovic was still apologetic in his post-match interview.
"I'm not being offended or mistreated by anybody. I don’t really pay too much attention on that,” he said. “I like to respect others. I hope that others can respect me and my decision.
“I’m sorry for the crowd. Obviously they came to see a full match, and just wasn’t to be. That’s all it is.
“I mean, a lot of people didn’t know what’s happening, so you cannot blame them. It is what it is.”News Now - Sport News