No.4 seed and Wimbledon champion Simona Halep was a 6-4, 6-1 victor in her only previous meeting against lucky loser Nicole Gibbs, in the first round of Shenzhen last year. In the Open Era, only one Wimbledon champion has gone on to lose in the first round of the US Open that year (Petra Kvitova, who lost to Alexandra Dulgheru in 2011) and only one SW19 winner has fallen to a qualifier or lucky loser in New York (Kvitova again, who lost to Aleksandra Krunic in 2014). In eight previous meetings against Top 10 opposition, Gibbs has won two sets - the last of which was also at the US Open, a 2-6, 6-3, 6-4 third-round loss to Karolina Pliskova in 2017.
Defending champion Naomi Osaka takes on Anna Blinkova for the first time in her first-round match. Only two US Open defending champions have fallen at the first hurdle in the Open Era, Svetlana Kuznetsova in 2005 (to Ekaterina Bychkova) and Angelique Kerber in 2017 (to Osaka herself). Blinkova, the 2015 Wimbledon girls' finalist, owns two career Top 20 wins - but none over a Top 10 player yet.
An all-Belarusian first-round tilt finds No.9 seed Aryna Sabalenka facing Fed Cup teammate and 2012-13 runner-up Victoria Azarenka for the first time. Azarenka is 3-1 against compatriots at Tour level, with the only loss coming via retirement to Olga Govortsova in the first round of Hobart in 2008; meanwhile, this will be the first time that Sabalenka has played a countrywoman at Tour level.
No.7 seed Kiki Bertens faces lucky loser and 2015 Roland Garros girls' champion Paula Badosa for the second time in the past two months. Their first meeting in July saw Bertens defeating the Spaniard 6-1, 7-5 in the Palermo semifinals.
No.15 seed Bianca Andreescu is making her US Open main draw debut, having lost in the first round of qualifying on both her previous appearances in Flushing Meadows - to Liu Fangzhou in 2017 and to Olga Danilovic in 2018. The 19-year-old Canadian opens against 17-year-old wildcard and Grand Slam debutante Katie Volynets, whom she defeated 6-2, 7-6(7) in the second round of the Newport Beach 125K event in January en route to lifting the trophy.
2016 Wimbledon girls' champion Anastasia Potapova squares off against 2018 Roland Garros girls' champion Coco Gauff for the first time in a clash of rising youngsters. 15-year-old Gauff is 3-1 against fellow teenagers this season, having defeated Ashley Kratzer and Ann Li in ITF events and Catherine McNally on her WTA debut in Miami, but lost to Kaja Juvan in Roland Garros qualifying; 18-year-old Potapova is 0-3 against other teens in 2019 after losing to Marketa Vondrousova twice (in Budapest and Roland Garros) and to Amanda Anisimova in Rome qualifying.
No.19 seed Caroline Wozniacki beat Wang Yafan 6-3, 6-1 in their only previous encounter in the first round of Kuala Lumpur in 2015 - the second WTA main draw of Wang's career - en route to winning her 23rd title.
No.28 seed Carla Suárez Navarro, quarterfinalist here in 2013 and 2018, is 4-0 against qualifier Timea Babos, having defeated the Hungarian on hard courts, grass and clay - at Florianopolis 2014, Birmingham 2015, Madrid 2016 and the Australian Open 2018. However, the last three of those encounters all went to a deciding set.
No.24 seed Garbiñe Muguruza leads her head-to-head against Wimbledon quarterfinalist Alison Riske 2-1. The Spaniard won their first two matches, in the second rounds of Birmingham 2017 and Monterrey 2018, in straight sets, but Riske scored a 6-1, 6-2 victory in their most recent meeting in the second round of Tokyo last year.
Aleksandra Krunic owns three victories over seeded players in New York - Petra Kvitova and Madison Keys in 2014, and Johanna Konta in 2017 - and defeated former Roland Garros champion Jelena Ostapenko in their only previous meeting, also on American hard courts, 6-4, 6-2 in the first round of Cincinnati in 2017.
ORDER OF PLAY
For full order of play, visit usopen.org.
Serena Williams's 59-minute dismissal of Maria Sharapova was a "throwback", writes Tumaini Carayol in The Guardian - and may help her rediscover her dominance going forwards.
As tempting as it may be to buy into first-week form, Matt Zemek reminds us at Tennis With An Accent that it would be a mistake to write off players beneath their best - as long as they're winning.
The nascent friendship between Naomi Osaka and Iga Swiatek was borne out of mutual respect after their Toronto clash - and in New York, their promised practice session is paying off for the Polish teenager, writes WTA Insider Courtney Nguyen.
Former Roland Garros junior champion Paula Badosa is to make her US Open debut today - and the 21-year-old opened up to David Kane for wtatennis.com about the mental health struggles she's experienced in her pro career.