Wimbledon champion Elena Rybakina suffered a shock defeat by qualifier Clara Burel in the US Open first round.

Seeded 25th in New York, the 23-year-old was beaten 6-4 6-4 by world number 131 Burel.

Earlier on Tuesday, world number one Iga Swiatek won in straight sets.

Two-time US Open champion Naomi Osaka is out after losing 7-6 (7-5) 6-3 to American 19th seed Danielle Collins.

Poland’s Swiatek, 21, needed just one hour and six minutes to beat the Italian 6-3 6-0 in New York and faces 2017 winner Sloane Stephens next.

American Stephens came back from 6-1 3-1 down to beat Belgium’s Greet Minnen 1-6 6-3 6-3.

Two-time French Open winner Swiatek is one of several female players to complain about the “horrible” balls being used at Flushing Meadows.

The US Open is the only major where men and women use different balls.

Rybakina loses out on court 12

Moscow-born Rybakina, who now represents Kazakhstan, would have moved into the world’s top eight if ranking points – which were stripped because Wimbledon had banned Russian and Belarusian players – had counted.

With her ranking instead down at 25, she was scheduled on the relative obscurity of court 12 in New York.

Burel, 21, broke to go 3-2 up in the first set, before Rybakina levelled things at 4-4 but the Grand Slam winner was immediately broken again and her opponent served out the set.

The Frenchwoman was more dominant in the second set as Rybakina helped her opponent with a total of 37 unforced errors in the match.

Burel went 2-0 up and remained ahead until she claimed victory with a backhand down the line before raising her hands to the sky in relief at reaching the US Open second round for the first time.

Osaka’s bad run continues

Japan’s former world number one Osaka, 24, has had an inconsistent year on tour and has dropped to 44th in the world rankings, having missed the entire grasscourt season and losing in the first round in Toronto and Cincinnati.

A winner at Flushing Meadows in 2018 and 2020, she was unseeded this time and has not won back-to-back matches since a run to the Miami final in April.

“Honestly, I just wanted to play without my back being in pain because it’s kind of been bad for the entire hard court season since Toronto,” said Osaka. “I didn’t serve until two days ago so I was really happy with how it went.

“Everyone deals with injuries. For me, it’s been more prominent this year, but it’s something that I can learn (from).”

Collins, 28, lost to Ash Barty at the Australian Open in January, but had not played since July because of a neck injury.

“I lost to Naomi three times before, so going into the match I had a lot of information on what I needed to do better, areas I could improve,” said Collins, who will play Spain’s Cristina Bucsa in the next round. “I felt happy just to be out here playing.

“I think when you face as many challenges as I’ve faced with some of the things I’ve been dealing with, you’re more grateful to be out here.”

Venus Williams exits in first round

There will be only one Williams sister in the singles second round in New York after Venus Williams was beaten 6-1 7-6 (7-5) by Belgium’s Alison van Uytvanck.

Making her 91st Grand Slam singles main draw appearance, the 42-year-old could not follow in younger sibling Serena’s footsteps in progressing on Arthur Ashe Stadium.

Williams, the US Open champion in 2000 and 2001, committed three double faults and hit 13 unforced errors as Van Uytvanck dominated the first set, but found her feet in the second to force a tie-break – though her efforts eventually proved fruitless.

The Williams sisters will team up in the women’s doubles for what is expected to be the last time as younger sister and 23-time Grand Slam singles champion Serena prepares to “evolve away” from tennis, while Venus’ future in the sport remains unknown.

Asked after her defeat if she too might be preparing to evolve away from the sport, Venus replied: “Right now I’m just focused on the doubles.”

Van Uytvanck will face Rybakina’s conqueror Burel in the next round.

Muguruza through, Ostapenko out

Spanish ninth seed Garbine Muguruza also reached the second round, beating Dane Clara Tauson 6-3 7-6 (7-5), while 16th seed Jelena Ostapenko was defeated 6-3 3-6 6-4 by Chinese world number 39 Qinwen Zheng.

American 24th seed Amanda Anisimova, a Wimbledon quarter-finalist, fell at the first hurdle here, losing 6-3 6-3 to Kazakhstan’s Yulia Putintseva, while 2020 Australian Open champion Sofia Kenin of the United States was beaten in straight sets by Germany’s Jule Niemeier.

There will be no shortage of Czech representation in the second round as 22nd seed Karolina Pliskova beat Poland’s Magda Linette 6-2 4-6 7-6 (10-8) to set up a match against Marie Bouzkova.

Petra Kvitova, seeded 21st, joined them by powering through the second set to beat Russian Erika Andreeva 7-6 (7-3) 6-0, while 17-year-old Czech Linda Fruhvirtova will face Muguruza in the first Grand Slam second-round match of her career.

American eighth seed Jessica Pegula was a 6-2 6-2 victor over Viktorija Golubic and will next play Belarusian Aliaksandra Sasnovich, while fourth seed Paula Badosa of Spain is also through to the second round after a 3-6 7-6 (7-4) 6-3 win over Ukraine’s Lesia Tsurenko.

Olympic champion Belinda Bencic, the 13th seed, came through a tough battle against former French Open semi-finalist Andrea Petkovic, who is set to retire from the sport.

Swiss Bencic, who received a warning from the umpire after narrowly missing a ball boy when she through her racquet, won 6-2 4-6 6-4.

Three-time US Open finalist Victoria Azarenka of Belarus withstood a fightback from American Ashlyn Krueger, winning 6-1 4-6 6-2 to set up a second-round encounter with Ukraine’s Marta Kostyuk.

Last week Azarenka was due to play in a Tennis Plays for Peace exhibition in New York to raise humanitarian aid for Ukraine but did not take part, with Kostyuk among the Ukrainian players who were unhappy about her proposed participation.

Belarus is a close ally of Russia and its leader Alexander Lukashenko has supported Russia’s invasion of Ukraine.

Russian and Belarusian players were banned from Wimbledon this year but are being allowed to take part in the US Open under a neutral flag.