A visibly shattered Nick Kyrgios conceded he was "heartbroken" by being bundled out of the US Open in a quarter-final loss to Karen Khachanov. And, for the first time in his decade-long career, the Aussie enigma conceded winning grand slams is now the only thing that will quench his sporting thirst. Kyrgios is nearing the end of what has been his best season on tour. His round-of-16 exit at Flushing Meadows followed a maiden grand slam final appearance at Wimbledon, where he lost to Novak Djokovic. READ MORE: Kyrgios obliterates racquet in meltdown after quarter-final lossREAD MORE: 'Untenable' Hasler set for Manly showdownREAD MORE: Cleary defends 'great kid' after Panther's bizarre banBut he failed to see any positives after losing in five sets, having been the bookmakers' favourite to win in New York following the departures of Daniil Medvedev and Rafael Nadal from the tournament draw. "I feel like shit. I feel like I've let so many people down," Kyrgios told media after losing to Khachanov. "I feel like these four tournaments are the only ones that are ever gonna matter, and it's like you have to start it all again, and I have to wait until Australian Open. "It's devastating. It's heartbreaking. "Not just for me, it's for everyone I know that wants me to win. "Watch the US Open live and free on 9Now and every point from every match ad-free, live and on demand on Stan Sport. Kyrgios, 27, is undoubtedly in the midst of a career-best run of form this year. But his talent has never been in question. It is his application and appetite to succeed that tennis fans Down Under have struggled to get a read on since watching the tenacious kid from Canberra beat Rafael Nadal at Wimbledon in 2014. But since he shocked the All England Club to qualify for his first grand slam final earlier this year, supporters have noticed a change in attitude from Kyrgios. He's no longer on tour to simply collect a paycheque. He now wants to win major titles - and nothing else will be good enough. "Honestly I don't even really care about any other tournament," Kyrgios said after his US Open loss. "I feel like at the grand slams, now having success at a grand slam, it's like no other tournament really matters. "It's like you get better, you get worse, and then at a grand slam none of it matters, you only win or lose. "People don't care whether you got better on the day, or you lost (6-4) in the fifth, or you played one of the best matches of the tournament - you lost. "That's all people remember at a grand slam, whether you win or you lose, and I think 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. "Kyrgios would not answer whether he plans to play any more tournaments this year. He will fly home to Canberra where his parents have been ill. He did, though, as much as confirm his intention to contest the Australian Open in January. For a daily dose of the best of the breaking news and exclusive content from Wide World of Sports, subscribe to our newsletter by clicking here!.