The leading seeds had another tremendously successful day as the first round of US Open qualifying concluded on Wednesday at the Billie Jean King USTA National Tennis Center in Flushing Meadows, NY.

After all five Top 10 seeds in action on Tuesday won their opening-round matches, the remaining five Top 10 seeds also went undefeated on Wednesday as the field of 128 was whittled down to 64.

16 spots are available for qualifiers into the main draw -- as well as at least three more spots for lucky losers, following the unfortunate withdrawals of six-time US Open champion Serena Williams, her sister two-time US Open champion Venus Williams, and 2020 Australian Open champion Sofia Kenin.

No.1 seed Ana Konjuh of Croatia led the field into the second round. The World No.87, who is having a resurgent season after years of recurring injuries, ousted Irina Fetecau of Romania, 7-6(2), 6-3, to win her first match of the week.

Konjuh had the best Grand Slam performance of her career to date at the 2016 US Open, where she reached the quarterfinals as an 18-year-old. That result helped her reach a career-high ranking of World No.20 in 2017 before she was set back by constant elbow injuries and surgeries.

This season, the Croat is back to winning ways, reaching her first WTA singles final in four years in Belgrade, and recently returning to the Top 100. But Konjuh was tested by Fetecau, with a 15-minute opening game that featured 11 deuces setting the stage.

Nevertheless, top-seeded Konjuh ultimately won 71 percent of her first-service points, compared to Fetecau's 56 percent success rate behind that shot, and she gritted past the Romanian in an hour and 39 minutes.

No.4 seed Mayar Sherif of Egypt also advanced into the second round after beating 15-year-old American wildcard Clervie Ngounoue, 6-4, 6-3, in an hour and 22 minutes. Sherif converted five of her eight break points to quell the challenge by the rising American teen.

Sherif has also had a breakthrough summer in 2021, becoming the first Egyptian to crack the Top 100 of the WTA singles rankings mere weeks ago, after she reached her first WTA singles final in Cluj-Napoca.

No.5 seed Oceane Dodin also booked her spot in round two. The big-hitting Frenchwoman, who cracked the Top 50 in 2017, needed only 59 minutes to defeat Jessica Pieri of Italy, 6-1, 6-3.

Also on Wednesday, No.8 seed Kristina Kucova of Slovakia ousted Chile's Daniela Seguel, 6-3, 6-2, and No.9 seed Maryna Zanevska of Belgium knocked out Asia Muhammad of the United States, 6-4, 6-3.

Kucova and Zanevska are just a month removed from their battle for the Gdynia title, where Zanevska overcame Kucova in the first WTA singles final for either of them.

In other Day 2 results, No.11 seed Kristyna Pliskova of the Czech Republic beat Russia's Valeria Savinykh, 6-2, 6-1 in 53 minutes, and No.18 seed Stefanie Voegele of Switzerland eased past Whitney Osuigwe of the United States, 6-2, 6-2.

Wednesday also went perfectly for Great Britain, as their players went 4-0 on the day. No.31 seed Emma Raducanu opened with a 6-1, 6-2 victory over Bibiane Schoofs of the Netherlands, while No.32 seed Harriet Dart outlasted American Peyton Stearns, 6-3, 4-6, 6-3.

Read more: Out of the spotlight, Raducanu engineers career surge in U.S.

Unseeded Brits Katie Boulter and Jodie Burrage also claimed wins over Americans. Boulter ousted Gabriella Price, 6-3, 6-2, and Burrage defeated Robin Montgomery, 6-4, 6-1.