|Venue: Flushing Meadows, New York Date: 30 August-12 September|
|Coverage: Daily radio commentaries on BBC Radio 5 Live Sports Extra/BBC Sport website and app, with selected live text commentaries and match reports on the website and app|
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 capitalised 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.”
Fernandez keeps cool – as Osaka loses hers
Osaka has had a difficult past few months and took an eight-week break to protect her mental health after speaking openly about her struggles with depression.
She has had limited time on court, playing just five matches in the past two months, and received a walkover into the third round in New York after her opponent withdrew.
For the first set and for the majority of the second, Osaka looked in control, despite Fernandez matching her with her forehand and strong serving.
Serving for the match at 6-5, Osaka lost her rhythm, handing Fernandez a crucial break as she sent a forehand long.
The tie-break quickly went away from the two-time US Open champion, Osaka gesturing at herself and the court as the crowd rallied behind her opponent.
World number 70 Fernandez was a complete contrast to Osaka, celebrating her strong shot play and pumping the air as a miss down the line from Osaka sent the match to a decider.
Osaka spent the third set changeovers with a towel over her head, trying to regain her composure, but her frustration was still evident as she went down an early break and had to stave off two break points to avoid going 3-0 down.
While she showed glimpses of her best form, she could not force a break point on the Fernandez serve, with the teenager feeding off the crowd.
Osaka was booed as she made Fernandez wait with the teenager 30-0 up and serving for the match, but the Canadian responded with a drop shot winner to garner three match points. She needed just one, turning and celebrating as Osaka sent a cross-court forehand wide.
BBC tennis correspondent Russell Fuller
Just hours after 18-year-old Carlos Alcaraz knocked out Stefanos Tsitsipas, another teenager thrilled Arthur Ashe Stadium with a daring and composed performance.
A tight and high quality match looked to be heading Osaka’s way when she stepped up to serve for a straight-set victory at 6-5. But at that point the defending champion’s forehand deserted her, and her frustration bubbled over.
Osaka is short of matches – having taken a break from the sport to preserve her mental health – but started to look threatening again after losing her serve early in the deciding set.
But it proved to be too late. Fernandez’s lefty serve had caused Osaka problems all night, and helped by some thumping returns, the Canadian did not pass up her opportunity.
Halep overcomes ‘crazy on court’
Romanian 12th seed Simona Halep rediscovered some of her pre-calf injury form with a battling 7-6 (13-11) 4-6 6-3 win over Elena Rybakina of Kazhakstan.
Playing with her right thigh heavily strapped, Halep saved three set points in the first set tie-break and had to fight back from a break down in each set.
“Before the match, I was super stressed and I told [her coach] Darren Cahill that my forehand is lost. So I cannot feel it anymore,” Halep said.
“I had emotions. I was nervous. And I was crazy a little bit on court, as well, the frustrations got me a little bit.
“But I fought, and this victory gives me a lot of confidence that my game is coming back and also the fighting spirit is there.”
She will face fifth seed Elina Svitolina next after the Ukrainian beat Russia’s Daria Kasatkina 6-4 6-2.
Garbine Muguruza earlier won the battle of Grand Slam champions as she beat Victoria Azarenka to reach the fourth round.
Both players have won Slam titles and are former world number ones but it was Spaniard Muguruza who edged out Belarus’ Azarenka 6-4 3-6 6-2.
It is the first time Muguruza, who will play French Open champion Barbora Krejcikova next, has reached the fourth round at Flushing Meadows.
Roland Garros champion Krejcikova continued her astonishing season with a 6-4 6-2 win over Kamilla Rakhimova of Russia.
Belgian Elise Mertens beat Tunisia’s Wimbledon quarter-finalist Ons Jabeur 6-3 7-5 to set up a meeting with either second seed Aryna Sabalenka or home favourite Danielle Collins.