Novak Djokovic is back at world number one after beating Alexandre Muller in straight sets and Iga Swiatek began her title defence by dropping only one game against Rebecca Peterson.

Britain’s Lily Miyazaki made a mark on her Flushing Meadows debut to reach round two.

Here, the PA news agency looks back at day one at the US Open.

Pic of the day

Former first lady Michelle Obama joined a ceremony to honour former champion and equality campaigner Billie Jean King, and celebrate 50 years since the US Open offered equal prize money to men and women.

Match of the day

Coco Gauff came from a set down in a thriller under the lights on Arthur Ashe against German qualifier Laura Siegemund. The American teenager, seeded sixth, eventually came through 3-6 6-2 6-4.

Shock of the day

Holger Rune tweeted a map of the Flushing Meadows site to highlight his frustration at being shoved out on Court Five. The Danish fourth seed’s irritation was clear as he slumped to a four-set defeat to Spaniard Roberto Carballes Baena.

Stench of the day

It’s a hard court, not grass, but eighth seed Maria Sakkari complained to the umpire about the smell of “weed” wafting through the air during her surprise defeat by Rebeka Masarova.

Brit watch

Lily Miyazaki branded her US Open debut “surreal” after winning her first match at a grand slam.

There were echoes of Emma Raducanu after the 27-year-old qualifier, Britain’s sole representative on day one, beat Russian Margarita Betova 6-3 6-3.

“It’s huge for me, I think,” said Miyazaki. “Qualifying was also, like, obviously a huge confidence booster, but winning at the main draw, it just feels a bit surreal.”

The world number 199 may be unlikely to emulate Raducanu’s fairy-tale title win two years ago, but she still secured a near-£100,000 pay day and a high-profile second-round match against Olympic champion Belinda Bencic.

Fallen seeds

Women: Maria Sakkari (8), Veronika Kudermetova (16), Anhalina Kalinina (28), Elisabetta Cocciaretto (29).

Men: Holger Rune (4), Felix Auger-Aliassime (15), Lorenzo Musetti (18), Alexander Bublik (25), Sebastian Korda (31).

Who’s up next?

Day two sees the other six British hopefuls begin their campaigns. Former champion Andy Murray will be on the Grandstand Court against Frenchman Corentin Moutet. Cameron Norrie, Dan Evans, Jack Draper, Jodie Burrage and Katie Boulter are also in action along with defending champion Carlos Alcaraz.

Elina Svitolina is in position to win her first title of 2021 after outlasting Rebecca Peterson to reach the Chicago Women's Open final. 

After dropping just one game in her quarter-final win over Kristina Mladenovic, Svitolina needed nearly two and a half hours to dispatch Peterson 6-1 6-7 (4-7) 6-3 on Friday.

The top seed will seek her 16th career WTA Tour title against ninth-seeded Alize Cornet, who rallied to defeat Varvara Gracheva 4-6 6-1 6-0 in the other semi. 

Gracheva's capitulation after winning the first set was understandable, as earlier in the day she had finished off a quarter-final upset of eighth seed Marta Kostyuk in a match that had been suspended due to darkness Thursday. 

Gracheva prevailed 6-7 (4-7) 6-3 6-4 in that contest, with play on Friday beginning late in the second set, but did not have enough to pull out another win. 

The final will feature the eighth head-to-head meeting between Svitolina and Cornet, with the Ukrainian holding a 4-3 edge. 

At Tennis in the Land, second seed Anett Kontaveit defeated seventh seed Sara Sorribes Tormo 6-4 6-4 in one semi-final. 

She will meet Irina-Camelia Begu in the final of the Cleveland tournament after the unseeded Romanian upset sixth seed Magda Linette 7-6 (7-5) 6-2. 

Kontaveit won her first WTA title at Guadalajara earlier this year, while Begu will be seeking her fifth Tour title and first since 2017.

Ashleigh Barty described her retirement from Thursday's second-round clash against Magda Linette at the French Open as "heartbreaking". 

Top seed Barty required medical attention during her first-round win over Bernarda Pera two days earlier, with a hip injury the cause for concern.

The 25-year-old – back at Roland Garros for the first time since winning her maiden grand slam title in Paris in 2019 – vowed to "play through the pain barrier", yet the injury prevented her from continuing when 1-6 2-2 down against her Polish opponent, who will face Ons Jabeur in the next round. 

The Australian's retirement throws the draw wide open, with both of the top seeds now out after Naomi Osaka decided to withdraw amid her disagreement with tournament organisers.

Barty's clay-court season ended with a title in Stuttgart, a runner-up finish in Madrid and an appearance in the quarter-finals in Rome, and she could scarcely hide her disappointment at the way things ended for her in the French capital. 

"It's heartbreaking," she told a media conference. "I mean, we have had such a brilliant clay-court season, and to get a little bit unlucky with timing and have something acute happen over the weekend and just kind of run out of time against the clock is disappointing. 

"It won't take away the brilliant three months that we have had, as much as it hurts right now.

"We did everything, absolutely everything we could to give myself a chance. It was a small miracle that we were able to get on court for that first round.

"I just tried to give myself a chance and see how it felt. Obviously practicing, we've had our restrictions and essentially tried to stay as fresh as possible and not aggravate it in any way, but in a match that's unavoidable at times.

"It got worse today and it was becoming at the stage where it was unsafe. As hard as it is, it had to be done. Right from the first game, I was battling the pain, and it just became too severe."

SVITOLINA CRUISES THROUGH, PLISKOVA DUMPED OUT

Fifth seed Elina Svitolina booked a third-round meeting with Barbora Krejcikova after seeing off Ann Li 6-0 6-4. 

Svitolina landed 74 per cent of her first serves and struck 10 winners to cruise past the American in the opening set. 

Li bounced back in the second, roaring into a 4-1 lead, but Svitolina clawed her way back to ensure she reached at least the third round in seven of her nine appearances at Roland Garros. 

Svitolina, who overturned a 2-5 deficit in the second set to beat Oceane Babel in the first round, said: "In the end, what I'm really happy with is the way that I was down in both matches in the second set and found a way. 

"I found a good level and didn't give up on the second set. That was a really good point for me, and I was really playing composed in both matches. It was two different players, but I was really happy that I could win in two sets in both matches."

Up next is Krejcikova, who overcame Ekaterina Alexandrova 6-2 6-3.

There is no place in the third round for ninth seed Karolina Pliskova, who was soundly beaten 7-5 6-1 by Sloane Stephens, while number 13 seed Jennifer Brady battled past Fiona Ferro 6-1 1-6 6-4. 

KENIN WINS BATTLE OF THE AMERICANS

Fourth seed Sofia Kenin defeated fellow American Hailey Baptiste, a qualifier who won four matches in Paris on her French Open debut, 7-5 6-3. 

Kenin will now face another compatriot in 28th seed Jessica Pegula, who beat Tereza Martincova 6-3 6-3.

Elsewhere, defending champion Iga Swiatek thumped Rebecca Peterson 6-1 6-1, Coco Gauff got the better of Wang Qiang 6-3 7-6 (7-1), and Elise Mertens edged out Zarina Diyas 6-4 2-6 6-4.