Naomi Osaka’s US Open title defence is over as she fell in the third round to a stunning performance by Canadian teenager Leylah Fernandez.

The 18-year-old Fernandez capitalized as Osaka lost her cool to craft a remarkable 5-7 7-6 (7-2) 6-4 victory.

Osaka was broken as she served for the match in the second set, and a poor tie-break handed Fernandez the initiative under the New York lights.

The teenager could not contain her smile as she secured a fantastic win.

Osaka never regained her composure after she was broken in the second set, twice throwing her racquet to the floor as the tie-break flew away from her.

Fernandez broke her in the opening game of the third set and used her powerful forehand to muscle her way to victory.

She will face another Grand Slam champion in Angelique Kerber in the fourth round.

“From the very beginning I knew I was able to win,” Fernandez said.

“I wasn’t focusing on Naomi, I was just focusing on what I needed to do. The crowd made a huge difference – they helped me get the win.”