Novak Djokovic retired three games into the third set after dropping the first two to Stanislas Wawrinka in the fourth round of the US Open on Sunday night.
Djokovic, who was seeded No. 1 and seeking a fourth championship in New York, has been bothered by a shoulder injury throughout the tournament.
Wawrinka, seeded No. 23 in the tournament, won the first two sets 6-4, 7-5 to take a large lead against Djokovic as he sought to beat him in their first meeting since the 2016 US Open final. Wawrinka had just won a game to go up 2-1 in the third set when Djokovic decided not to continue.