The 2023 US Open got underway with play in the top half of the women's draw as defending champion Iga Swiatek headlined the winners on opening day.
Among those joining the Pole in the second round were fourth seed Elena Rybakina sixth seed Coco Gauff and tenth seed Karolina Muchova.
Eighth seed Maria Sakkari, 16th seed Veronika Kudermetova, 28th seed Anhelina Kalinina and 29th seed Elisabetta Cocciaretto were upset victims.
Swiatek, Rybakina, Muchova cruise; Gauff gets by Siegemund; Masarova stuns Sakkari
Swiatek kicked off her title defense with a 6-0, 6-1 thrashing of Rebecca Peterson. The Pole improved to 3-0 lifetime against the Swede and hit 20 winners in the 58-minute contest.
In what was thought to be one of the toughest first-round matchups in the entire draw, Rybakina easily handled Marta Kostyuk on Grandstand.
Needing just 58 minutes to dispatch the Ukrainian, the 2022 Wimbledon champion converted on five of 12 break points to avenge a loss earlier this season to Kostyuk in Adelaide.
The US Open is the only major where Rybakina has not reached at least the quarterfinals with a third-round appearance in 2021 her best previous result.
For Gauff, she had to dig deep in a 3-6, 6-2, 6-4 marathon win over German qualifier Laura Siegemund.
In the two-hour, 51-minute contest on a night when 50 years of equal prize money was being celebrated with a pre-match ceremony, the American rallied from a set down and held on after Siegemund cut a 5-1 lead to 5-4.
Muchova was the first winner of the tournament as the Czech needed just 65 minutes to take care of Storm Hunter 6-4, 6-0.
Up a break twice in the first set, the Roland Garros and Cincinnati finalist watched the Australian wild card battle back both times, leveling the set at 4-4.
From there, Muchova, in the Top 10 for the first time in her career after her Cincinnati run, won the last 8 games to sweep into the second round.
Up next for her is Magdalena Frech who defeated American Emma Navarro.
Masarova scored her first top ten win in her fifth attempt with a 6-4, 6-4 victory over Sakkari.
Trailing 4-1 in the first set, the Spaniard won the final five games of the set to take the lead and she was never broken in the second set on her way to victory.
Anna Schmiedlova is Masarova's next opponent as she was a three-set winner over Kateryna Baindl.
Kvitova, Ostapenko lead other seeded winners
11th seed Petra Kvitova had an easy time with Cristina Bucsa, 15th seed Belinda Bencic, 18th seed Victoria Azarenka, 24th seed Magda Linette and 30th seed Sorana Cirstea were easy winners.
20th seed Jelena Ostapenko and 32nd seed Elise Mertens needed three sets to overcome Jasmine Paolini and Mirjam Bjorklund respectively.
American results
There were 11 American woman in action on Day One with Danielle Collins, Jennifer Brady, Bernarda Pera, Lauren Davis and Taylor Townsend joining Gauff in the winner's circle.
Collins dismantled Linda Fruhvirtova 6-2, 6-0 in just 52 minutes, never facing a break point while Brady, playing in her first major since Roland Garros in 2021, came from 5-3 down in the second set to record a 6-3, 7-6 (3) victory over Kimberly Birrell.
Townsend, the last player directly into the main draw, had an easy time with Varvara Gracheva, winning by a score of 6-4, 6-2 and Pera reached the second round in Flushing Meadows for the first time since 2020 with a 7-5, 6-4 upset over Kudermetova.
Sloane Stephens was edged out by 19th seed Beatriz Haddad Maia in just under three hours as the Brazilian claimed a hard-fought 6-2, 5-7, 6-4 win.
Clervie Ngounoue, Kayla Day and Katie Volynets joined Navarro and Stephens in being eliminated.
Other results
There were straight sets wins for Anna Kalinskaya over Katerina Siniakova, Lin Zhu, who defeated Mayar Sherif and Yuriko Miyazaki, who got by Margarita Betova.
Those winning in three sets were Elina Avanesyan, Xiyu Wang, Mirra Andreeva who rallied from a set down to defeat Olivia Gadecki and Alja Tomljanovic.
Finally, Caroline Wozniacki had no problems with Tatiana Prozorova in her comeback to the US Open, winning 6-3, 6-2.
Prozorova, ranked 227th in the world and making her debut at a major, made 41 unforced errors and was broken six times.