Tuesday officially kicked off the path to the year's final Grand Slam event, as US Open qualifying got underway in Flushing Meadows.

Following a 2020 edition with no qualifying tournament, 128 players are once again attempting to grit out three wins this week, in order to grab one of 16 coveted spots in next week's main draw in New York City.

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Half of the first-round matches took place on Tuesday, a day which turned out to be a great start for the top seeds. Five of the Top 10 seeds were in action on Day 1, and they all advanced to the second round.

No.2 seed Anna Karolina Schmiedlova of Slovakia, though, was pushed to the limit to make it through. Schmiedlova outlasted France's Tessah Andrianjafitrimo, 6-3, 4-6, 6-3, in a barnburner that took exactly three hours in the heat of the Billie Jean King USTA National Tennis Center.

Former World No.26 Schmiedlova let 15 of her whopping 22 break points fall by the wayside in the clash, but her seven successful breaks were enough to push her past Andrianjafitrimo by the end of a marathon encounter.

Schmiedlova's tough draw continues, as she will now take on another former Top 30 player, Lesia Tsurenko of Ukraine. Tsurenko, who reached the US Open quarterfinals in 2018 but has struggled with injuries since, edged Ellen Perez of Australia, 7-5, 7-6(2).

No.3 seed Nuria Párrizas Díaz of Spain had an easier time, defeating Croatia's Tereza Mrdeza, 7-6(4), 6-1. Párrizas Díaz made her Top 100 debut just this month at the age of 30, a few weeks after winning the WTA 125 event in Bastad.

No.6 seed Greet Minnen also eased into the second round, as the Belgian knocked out Andrea Lázaro García of Spain, 6-3, 6-2.

No.7 seed Elena-Gabriela Ruse of Romania needed two-and-a-half hours to advance, beating Paraguay's Veronica Cepede Royg, 6-2, 6-7(5), 6-3. Ruse reached two WTA singles finals this summer, winning her first title in Hamburg and finishing runner-up to Danielle Collins in Palermo.

Another of this year's first-time WTA singles titlists, No.10 seed Astra Sharma of Australia, won her first-rounder over Slovakia's Viktoria Kuzmova in two tough sets, 7-5, 7-6(5). This spring, Sharma defeated Ons Jabeur to capture her maiden title at the WTA 250 event in Charleston.

In other first-round results, former Top 30 player Urszula Radwanska of Poland knocked out No.27 seed Katarina Zavatska of Ukraine, 6-3, 7-5, and former World No.20 Mihaela Buzarnescu of Romania ousted Katarzyna Kawa of Poland, 6-3, 7-5.

Canada's Rebecca Marino, who had a stirring run to the round of 16 on home soil at the National Bank Open two weeks ago, started her qualifying campaign off with a win. Marino beat Hungary's Panna Udvardy, 6-3, 6-2.

Also, American wildcard Reese Brantmeier, the runner-up at this month's USTA Girls’ 18s National Championships, notched an upset in her first match, defeating No.21 seed Olga Govortsova of Belarus, 6-2, 6-3.