document: The 22-year-old 14th seed went down 6-3 1-6 6-4 6-1 in the first round in New York.
  Kyrgios looked to have taken control of the match before he hurt his shoulder in the third set.
  "One serve and my arm's totally dead," he told the physio while receiving treatment.
  "I don't know what to do. It's so dead and numb, it's incredibly weak. I wasn't feeling it at all, and all of a sudden, bang, with one serve."
  After dropping the first set to Millman, the world number 235, it appeared as though Kyrgios was on his way to victory when he took the second 6-1.
  However, the contest changed dramatically with Kyrgios serving at 1-1 in the third, at one point asking a ball boy to help him stretch his right arm.
  To add to his frustration, Kyrgios was given a warning for an audible obscenity and, after losing the third set, penalised a point for violently smashing his racquet.
  "My forehand's painful, it's just so annoying," he told the trainer.
  When fully fit, Kyrgios has shown the kind of form this year that has made him tipped as a possible Grand Slam champion, taking a rampant Federer to a final set tie-break in Miami and reaching his first Masters final in Cincinnati this month.
  "I don't know what to do, I really don't," he added on court.
  "I'm feeling good, I finally had a good week last week, playing a good match, middle of the third set against an Aussie, and bang - that's it."
  Millman goes on to face Tunisia's Malek Jaziri or Thiago Monteiro of Brazil in the second round.
  "I know Nick's shoulder deteriorated as the match went on, so it's a victory, but slightly hollow," said Millan. "I feel for him."
summary: Australia's Nick Kyrgios struggled with a shoulder injury as he lost to compatriot John Millman at the US Open - admitting: "I don't know what to do."