It's Grand Slam or bust for Nick Kyrgios, who was disappointed with his US Open quarter-final defeat to Karen Khachanov.

The Wimbledon runner-up succumbed in a five-set thriller to his Russian opponent, who reached the last four at a major for the first time.

The 27-year-old, who won the Australian Open men's doubles crown with Thanasi Kokkinakis, had looked strong to clinch his maiden men's singles Grand Slam in Flushing Meadows after knocking out defending champion Daniil Medvedev in the previous round.

During his post-match press conference, Kyrgios lamented how other titles practically did not matter if it was not a Grand Slam.

"After having success at a Grand Slam, it's just like no other tournament really matters. You get better, you get worse, and then in the Grand Slam, none of it matters.

"People don't really care if you got better on the day or you lost four in the fifth set or you played one of the best matches of the tournament and you lost.

"So that's all people remember at a Grand Slam, whether you win or you lose, and I think pretty much every other tournament during the year is a waste of time. You just front up and show up at a Grand Slam. That's what you're remembered by.

"I just feel like these four tournaments [Australian Open, French Open, Wimbledon, US Open] are the only ones that are ever going to matter [and now] I have to wait until the Australian Open.

"It's just devastating, it's heartbreaking, not just for me [but also] for everyone that I know [who] wants me to win," he said.