Novak Djokovic retired from his US Open match on Sunday after dropping the first two sets to Stan Wawrinka, sending the Swiss three-time Grand Slam champion into the quarter-finals.
Djokovic, was in pain from a nagging left shoulder injury while 34-year-old Wawrinka.
On a day when Roger Federer cruised into a quarter-final against Bulgaria´s Grigor Dimitrov and Russian fifth seed Daniil Medvedev reached his first Slam quarter-final, Djokovic´s shocker stole the show.
Djokovic admitted he has been hurting for weeks without detailing how or when the injury took place.
