NEW YORK, SEPTEMBER 05

Nick Kyrgios crushed world number one Daniil Medvedev's dreams of a title defense at the US Open on Sunday with a 7-6(11) 3-6 6-3 6-2 victory to reach the quarter-finals and ensure there will be a new top-ranked player when the tournament concludes.

In a meeting worthy of a Broadway show between two of the game's biggest servers and most combustible personalities, it was the fiery Australian who was the better in the match's biggest moments, showing off a renewed focus and fitness.

"It was an amazing match," Kyrgios said in an on-court interview before a sold-out crowd at Arthur Ashe Stadium.

"Daniil is the defending champion so there's a lot of pressure on his shoulders, but I played really well. I've been playing amazing the last couple months and what a place to do it, packed house in New York.

"I'm extremely blessed."

Kyrgios delights in shunning the norms of tennis and did so again in a bizarre moment early in the third set when he ran around the net to hit a ball that Medvedev had sent high in the air, leading Kyrgios to celebrate enthusiastically.

The play cost Kyrgios the point but seemingly raised his spirits as he would break for 3-1 and take the set with a perfectly executed drop shot.

In the fourth, Kyrgios again broke early for a 2-1 lead he would not relinquish and Medvedev began to crumble from there, hitting balls against the back wall in frustration as the match grew further out of reach.

"I still can't believe the boneheaded play I made over here," Kyrgios said of the play where he crossed over to Medvedev's side.

"I thought that was legal to be honest. That's going to be everywhere on SportsCenter so I'm going to look like an idiot but that's alright."

Medvedev, who dropped to 1-4 lifetime against Kyrgios, tipped his hat to him after the match and admitted to struggling in the stifling heat and humidity.

"I felt my throat a little bit today," he told reporters.

"I think that physically maybe that played a little bit of a role. At the same time it's not an excuse at all because Nick played good."

Wimbledon finalist Kyrgios is playing the best tennis of his life, recording the most wins on tour since the end of the French Open and his quarter-finals appearance marks his best results at the Grand Slam tournament in Queens.

"I'm just trying to work hard every day, try to make every practice session count, getting to sleep," he said.

"I would have probably been out every night before but now I've got a great girlfriend. She helps me, and my team."

The 23rd-seeded Kyrgios will be a heavy favourite when he plays another Russian, 27th seed Karen Khachanov, on Tuesday.