It was the new Nick Kyrgios experience. 

His typical histrionics — from slamming his racket and yelling at his box to nearly getting himself disqualified by almost rocketing the ball into the crowd and arguing with the chair umpire — and brilliant tennis. 

Kyrgios still struggles with immaturity, his focus straying and his patience lacking, but he has begun to learn how to harness it. Sunday night was an apt example as the controversial Australian pulled off the biggest upset of the U.S. Open thus far in defeating last year’s champion. 

The 23rd-seeded Kyrgios ousted No. 1 Daniil Medvedev at Arthur Ashe Stadium in four sets, 7-6 (13-11), 3-6, 6-3, 6-2, and in doing so, knocked the Russian from his perch as the world’s No. 1. Kyrgios, meanwhile, is building momentum after his stunning run to the Wimbledon final to advance to his first ever U.S. Open quarterfinal. 

“I hadn’t won a match on Ashe before this week, now I’ve won two against two quality opponents,” Kyrgios said. “I feel like I’ve been able to showcase [my ability]. There’s a lot of celebrities here, a lot of important people here watching. I wanted to get on that court and show them I am able to put my head down and play and win these big matches. 

“For the tennis world I think it’s important as well. People were really starting to doubt my ability to pull out matches like this at majors. I’m really proud of myself honestly because it hasn’t been easy dealing with all the criticism.” 

The 27-year-old Kyrgios got better as the match progressed, facing just one break point on his serve in the final two sets after surviving a marathon first set tiebreak that saw him twice fling his racket to the court. Early in the third set, a frustrated Kyrgios smashed a dead ball against the wall that could’ve been a disqualification if had gone just a bit higher and hit a fan. Kyrgios cost himself a break point later in the set by oddly stepping over the other side of the court to hit a live ball. It drew boos from the large crowd. 

“I thought it was legal,” Kyrgios said, drawing laughs in his on-court interview, after defeating Medvedev for the fourth time in five meetings and second time in as many months. 

He won them over soon afterwards, and they repeatedly chanted, “Let’s Go Kyrgios,” as he found his form against the top-ranked player in the tournament. Kyrgios broke Medvedev three times in the last two sets, overwhelming the Russian with his power, deft touch at the net and surprising consistency. He had 21 aces and 53 winners altogether, and just 14 unforced errors over the final two sets. 

When Kyrgios broke Medvedev for the second time in the fourth set to go up 4-1, the result was inevitable. Kyrgios began shaking his head as they switched sides, like he knew Medvedev was done. 

“Obviously, Daniil is the defending champion, a lot of pressure on his shoulders, but I played really well,” Kyrgios said. “I’ve been playing amazing the last couple months.” 

His upset opens up the top half of the men’s draw, pitting him against No. 27 Karen Khachanov next. No. 5 Casper Ruud-No. 13 Matteo Berrettini will meet in one of the other quarterfinals. Nobody at the moment, however, is playing better than Kyrgios, who finally seems to be putting it together after years of frustrating teases. 

“I played Novak [Djokovic, Rafael Nadal]. They all play amazing,” Medvedev said. “Nick today played kind of their level, in my opinion. He’s tough to play. He has an amazing serve. … If he plays like this until the end of the tournament, he has all the chances to win it.”