A disconsolate Nick Kyrgios says he feels he has "let so many people down" after losing his US Open men's quarterfinal to Karen Khachanov in five sets.
With a semifinal berth at stake, Kyrgios seemed to lack the energy he displayed when he defeated world number one and defending champion Daniil Medvedev in the fourth round two days ago.
He effectively played catch-up for much of the match against Khachanov, with the Russian winning 7-5, 4-6, 7-5, 6-7 (3/7), 6-4 in three hours and 39 minutes.
Kyrgios's frustration was clear to see immediately after the match, with the Australian smashing two of his racquets on the court in front of a stunned Arthur Ashe Stadium crowd.
"I'm obviously devastated," Kyrgios later told his post-match media conference.
"But all credit to Karen. He's a fighter. He's a warrior. I thought he served really good today. Honestly, he's probably the best server I played this tournament, the way he was hitting his spots under pressure.
"He just played the big points well. There really wasn't anything in it. I'm just devastated, obviously. I just feel like it was either winning it all or nothing at all, to be honest.
"I feel like I've just failed at this event right now. That's what it feels like."
Despite achieving his best US Open result, Kyrgios said he wasted a golden opportunity to win his first major singles title.
"All people remember at a grand slam [tournament], is whether you win or you lose," he said.
"I think pretty much every other tournament during the year is a waste of time really.
"You should just run up and show up at a grand slam [tournament]. That's what you're remembered by."
Kyrgios on the back foot
After winning the fourth set in a tie-break, Kyrgios found himself on the back foot when he dropped serve in the opening game of the fifth.
He had break points during the deciding set, but each was saved by 27th seed Khachanov, who progressed to his first semifinal at a major.
"I tried to stay focused in the match," Khachanov said.
"I had some opportunities in the fourth set, but he played an amazing tie-break and what can I do? I can stay focused and try to win the next set.
"I'm really proud of myself. I was really focused from the beginning to the end and I got the win."
Kyrgios, seeded 23 in New York, had earlier received medical attention on his left knee prior to the start of the second set.
At one stage during the match, he loudly told his players box: "I don't want to play through this shit. I really don't want to f***ing do it."
Kyrgios had entered the US Open with the most wins on the men's tour since June.
Khachanov will play fifth-seeded Norwegian Casper Ruud in the semifinals.
