Defending champion Novak Djokovic is out of the US Open after quitting because of injury against Swiss 23rd seed Stan Wawrinka as defeat loomed in an electrifying fourth-round match.
Djokovic, 32, retired with a shoulder problem seconds after a double fault left him two sets and a break down.
Loud boos greeted the Serb’s decision, with more heard as he walked off court.
“I’m sorry for the crowd. They came to see a full match but it wasn’t to be,” said world number one Djokovic.
Three-time Grand Slam champion Wawrinka had dominated the last-16 contest in a boisterous atmosphere at Arthur Ashe Stadium, producing a powerful display reminiscent of his best to lead 6-4 7-5 2-0, when Djokovic decided he could not continue.
Wawrinka, 34, will play Russian fifth seed Daniil Medvedev in the quarter-finals.