The result means Medvedev will relinquish his position at the top of the world rankings at the end of the tournament, while Kyrgios will appear in his first US Open quarterfinal on Tuesday when he faces another Russian playing under a neutral flag, Karen Khachanov. , on Tuesday.
Medvedev later said he struggled physically on the field, but added that Kyrgios beat him in the last two sets.
“Today I felt a little sick,” he told reporters after the game. “The point is that in the US I definitely get sick in the swing once because the AC (air conditioning) is just crazy. Last year it happened in Cincinnati.”
“I felt my throat a bit today… At the same time, it’s no excuse at all, because Nick played well.”
It was the fourth time Kyrgios defeated Medvedev in five encounters and the second in as many months after the Montreal win.
The Australian saved several set points in a close tiebreak in the first set – the first set Medvedev had dropped in the tournament – before falling behind in the second set when he dropped the service twice.
Medvedev evened the game, but the momentum turned in Kyrgios’ favor as he won five straight points off Medvedev’s serve in the fourth game of the third set.
The 23rd seed always seemed to be the favorite to win the match from then on, breaking twice in the fourth set to seal the win in nearly three hours. He ended the meeting with 53 winners, 21 of which were aces.
“I just thought I was playing the right way,” Kyrgios told reporters. “I came back incredibly today. I thought the third and fourth set were just so free. I just had a lot of fun and embraced every moment in Ashe (Arthur Ashe Stadium) today. I’m really proud of that.”
“I feel like I’m more proud of the way I came back after all, honestly,” he said. “I’ve been in some really tough situations mentally, and some really scary places.
“Obviously when you look at it on paper, I probably didn’t expect to win that. Maybe I’ll take a set or two if I’m lucky… I’m just sitting there in the dressing room and I’m just super proud of the performance because there really was a time when I didn’t think I was capable of producing and doing this anymore.”