US Open 2017: Nick Kyrgios knocked out by John Millman

Nick Kyrgios hurt his shoulder early in the third set

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."

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."

Kyrgios retired from three consecutive tournaments earlier this summer and has struggled with his shoulder, hip and elbow in 2017 alone.

"I keep letting people down," he said, before suggesting that he was "not good enough" for coach Sebastien Grosjean.

"I'm not dedicated to the game at all," added Kyrgios. "He's helped me a lot, especially in training sessions.

"There are players out there that are more dedicated, that want to get better, that strive to get better every day, the one-percenters. I'm not that guy."

'I was less dedicated in Cincinnati'

Nick Kyrgios reached the Cincinnati Open final earlier this month, losing to Grigor Dimitrov

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.

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"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.

"In Cincinnati, I was not doing anything different," said Kyrgios.

"I was probably less dedicated than I was this week. I was playing basketball at Lifetime Fitness every day for two hours.

"Like I played an hour of basketball before I played David Ferrer in the semi-final. I was going to eat ice cream, like this Graeter's place getting a milkshake every day. I was less dedicated.

"And this week I was dedicated, and my shoulder starts hurting. I don't know."

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 Millman. "I feel for him."