Nick Kyrgios beats top seed Daniil Medvedevat at the US Open

Medvedev won his first Grand Slam title in New York last year but was surpassed on Sunday by Kyrgios, who is achieving career-best results – reaching the Wimbledon final in July and winning the Citi Open title in Washington in the last month .

The result means that Medvedev will cede his position at the top of the world rankings by the end of the tournament, while Kyrgios will compete in his first US Open quarterfinals when he meets another neutral-flagged Russian, Karen Khachanov, on Tuesday .

Medvedev later said he struggled physically on the court but added that Kyrgios outplayed him in the final two sets.

“I felt a bit sick today,” he told reporters after the game. “The thing is, I’m sure I’ll get sick at some point in the US because the air conditioning (AC) is just crazy. It happened in Cincinnati last year.”

“I felt my throat a little bit today… At the same time, it’s not an excuse at all because Nick played well.”

It was the fourth time Kyrgios had defeated Medvedev in five encounters and the second time in as many months after winning in Montreal.

The Australian saved several set points in a tight tiebreak in the first set – the first set Medvedev lost in the tournament – before falling behind in the second set when he lost serve twice.

Medvedev leveled the match but the momentum turned in Kyrgios’ favor as he won five straight points on Medvedev’s serve in the fourth game of the third set.

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The 23rd seedling always seemed the favorite to win the match from there, breaking twice in the fourth set to seal the win in nearly three hours. He ended the encounter with 53 winners, 21 of which were aces.

“I just thought I played right,” Kyrgios told reporters. “I hit back incredibly today. I just thought the third and fourth movements were just so free. I just had a blast and enjoyed every moment at Ashe (Arthur Ashe Stadium) today. I’m really proud of that.”

Unbeaten in nine games leading up to the US Open, Kyrgios employed a newfound focus and consistency on the pitch that has seen him have some notable success this season – something he attributes to overcoming mental challenges over the past few years .

“I feel like, to be honest, I’m rather proud of how I’ve recovered after everything,” he said. “I’ve been in some really difficult situations mentally and in some really scary places.

“Looking at it on paper, I probably wasn’t expected to win that. Maybe I’ll take a set or two if I’m lucky… I just sit in the dressing room afterwards and I’m just super proud of the performance because there really was a time when I didn’t believe I was able to to produce and do that.”