A somewhat subdued Nick Kyrgios has been knocked out of the US Open at the quarter-final stage as Russian Karen Khachanov won a 7-5 4-6 7-5 6-7 (3-7) 6-4 marathon.

On top of the world after defeating top seed Daniil Medvedev in the fourth round, the Australian was on the back foot immediately against Khachanov as he dealt with a calf injury.

“I can’t walk,” Kyrgios told his team.

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Kyrgios, who took a medical time-out to have his leg worked on, has played the most matches of anyone since June.

“I don’t want to f***ing play through this s***. I don’t want to play through it,” he added later as he threatened to revert to his old ways and give up on the match.

Nick Kyrgios needed treatment on a calf injury after the first set. Credit: Elsa/Getty Images

But the 27-year-old fought on and fought well for nearly four hours, breaking Khachanov in the third game of the second set and going on to level the match at one set all.

Neither player took full control in the third frame as Khachanov wasted two chances to win the set 6-4 on Kyrgios’s serve – only for Kyrgios to hit himself out of the set two games later.

The Aussie turned to the familiar tactic of venting to his box before smashing a bottle at the changeover, and letting off that steam almost worked.

He broke Khachanov for a 3-2 lead in the fourth – only to be broken the very next game.

Kyrgios threatened to move ahead 5-4 but the break point opportunity went begging, and on it went to a tiebreak that he dominated.

But Khachanov broke the Wimbledon runner-up in the opening game of the fifth set.

Kyrgios had four opportunities to break the Russian across three separate games but never managed to get across the line.