Nick Kyrgios has admitted he is “not dedicated to the game at all” after bowing out in the first round of the US Open.

The Aussie lost to compatriot John Millman in four sets at Flushing Meadows on Thursday morning (AEST) in a typically wild performance that featured smashed racquets, disputes with officials and an injury timeout.

Niggles have dogged Kyrgios in recent times, with the World No.18 now reporting injuries at his last five grand slams.

It was a shoulder injury that bugged him on this occasion, as Millman – ranked 218 places below him – won 6-3 1-6 6-4 6-1.

“My shoulder was hurting,” a frustrated Kyrgios said afterwards.

“I wasn’t feeling it at all and then on one serve I lost power in my arm. Just on my serve.

“One serve, then completely dead. It’s do dead and numb. It’s incredibly weak. It’s just so annoying.”

My coach is dedicated, I’m not

Kyrgios then went on to say he was “not good enough” for his new part-time coach, former French player Sebastien Grosjean, before speaking of his lack of dedication.

“I’m not good enough for him. He’s very dedicated. He’s an unbelievable coach,” he said.

“He probably deserves a player that is probably more dedicated to the game than I am. He deserves a better athlete than me.

“I’m not dedicated to the game at all. He’s helped me a lot, especially with the training, in training sessions, but there are players out there that are more dedicated, that want to get better, that strive to get better every day (do the) one-percenters. I’m not that guy.”

The brutally honest press conference continued when Kyrgios acknowledged his year was terrible from a grand slam point of view.

He won just two singles grand slam matches in 2017 despite being tipped to ‘breakout’ this year.

Thompson lost in another tight contest. Photo: Getty

“I have had a diabolical year at these slams. It doesn’t surprise me,” he said.

“It’s just the story of my career, really. I will have good weeks; I’ll have bad weeks. It’s just a rollercoaster.

“I don’t know. I don’t know. I keep letting people down.”

And when quizzed if he wanted to be extremely dedicated to his tennis, Kyrgios responded: “I really don’t know … probably not. Honestly not.”

Millman kept it simple, telling the press his win was “a victory, but a hollow victory”.

He added that he felt for Kyrgios, who has never made it past the third round at Flushing Meadows.

The news was not all bad for Aussies, though, as Ash Barty won through to the third round with a 6-1 7-6 (9-7) win over Belarusian Aliaksandra Sasnovich, while Daria Gavrilova also triumphed.

The 25th seed beat American Alison Kiick 6-2 6-1 in just 60 minutes to book a spot in the second round.

Jordan Thompson could not back up his five-set win over Jack Sock, going down in five to Thiago Fabbiano. The Brazilian won a topsy-turvy encounter 2-6 6-2 3-6 6-4 6-2.

Young gun Alex de Minaur was no match for sixth seed Dominic Thiem, who comfortably added the finishing touches to a 6-4 6-1 6-1 win that was spread over two days, while Arina Rodionova and Alja Tomljanovic also lost in straight sets.