No.21 seed Coco Gauff triumphed in a thriller on Louis Armstrong Stadium at the US Open on Monday, as the American teenager came back from a set and a break down to outlast Magda Linette of Poland, 5-7, 6-3, 6-4, and reach the second round.

In the first meeting between the pair, Gauff needed two hours and 34 minutes to fend off the challenge from 48th-ranked Linette, who is coming off a run to the Cleveland semifinals last week.

But Gauff did prevail, bettering her performance from last season, where she fell in the first round in Flushing Meadows to Anastasija Sevastova. Gauff reached the third round in her US Open debut in 2019.

Stat corner: The evenly-matched tilt saw the pair nearly level in unforced errors, but Linette well ahead on the winner count by 32 to 21. However, it was Gauff who was slightly more successful on the critical points, as she converted five of her 12 chances, while Linette went 4-for-13.

Key moments: Linette, to her credit, staged a stellar comeback of her own in the first set. Gauff served for the opener at 5-4, but Linette came out on top in grueling rallies to break back for 5-5, and the Polish player eventually won the final four games of that set to earn the initial lead.

But after falling behind a break in the very first game of the second set, Gauff found the range on her groundstrokes, with particularly purple patches from her backhand wing. Gauff broke Linette twice midway through the set to build a 4-2 lead and take home the set from there.

Gauff stormed to a 4-0 advantage in the decider before Linette took three games in a row to edge closer. But the American teen regrouped, coming up with clutch service points down the stretch before finishing the match with a volley winner.

Next up for Gauff: A difficult match against a seasoned compatriot awaits Gauff: she will next face former champion Sloane Stephens, after Stephens defeated fellow American Madison Keys via a third-set tiebreak in a rematch of the 2017 US Open final.

Coco says: "I was definitely very nervous coming into today's match just because it's a first round in your home Slam," Gauff told the media, after her win. "Honestly I'm glad that I was able to get through it. The crowd, playing in front of the New York fans, definitely is an experience that I'll never forget."

Gauff said that during the second set, "there definitely was a switch" in her level of play. "I think I focused more on having fun."

Looking ahead to her next opponent, Gauff, who has known Stephens since she was a young child, said: "Obviously [Stephens is] a very athletic player and super fast. I know I'm going to have to expect a lot of balls to come back. She's definitely going to redirect the ball. I think we're both ready. I think it will be an exciting match."

Kerber storms back for victory

2016 US Open champion Angelique Kerber also pulled off a stunning comeback to win her first-round match, as the German overcame Dayana Yastremska of Ukraine, 3-6, 6-4, 7-6(3).

In their only prior encounter, Yastremska beat former World No.1 Kerber via retirement en route to the 2020 Adelaide final. But Kerber was able to grit out an incredible victory this time around in nearly two-and-a-half hours, spoiling Yastremska's first Grand Slam match since 2020 Roland Garros.

No.16 seed Kerber led by a break twice in the first set, but Yastremska charged back each time, winning the final four games of the opener. However, Kerber leveled the match by taking the only service break in the final game of a much more serene second set.

An early flurry of breaks in the decider settled with Yastremska serving for the match at 5-4, but the Ukrainian dropped serve routinely and the players eventually moved into the tiebreak. There, three-time Grand Slam champion Kerber took control, leaping out to a 5-1 lead before clinching the topsy-turvy affair.

"In the third set, when we played the tiebreak, everything can happen," said Kerber, after the match. "I was just trying to staying focused, play every single ball as good as I can. I think that it was more for me that I won it mentally today. I'm happy about that, how I came back in the third set."

Kerber will next face another Ukrainian, Anhelina Kalinina. Kerber might remember Kalinina well, as Kalinina upset the German in the first round of Roland Garros earlier this year.

Victoria Azarenka in her first-round match at the 2021 US Open.

Photo by Andrew Ong/USTA

Azarenka, Svitolina advance into round two

Last year's runner-up Victoria Azarenka ended her first-round match with a torrid streak, reeling off the final 11 games to defeat Tereza Martincova of the Czech Republic, 6-4, 6-0.

Former World No.1 and two-time Grand Slam champion Azarenka needed an hour and 10 minutes to take down World No.60 Martincova and move into the second round in New York for the 13th time in her distinguished career.

No.18 seed Azarenka, who also reached the US Open final in 2012 and 2013 (falling to Serena Williams in both of those instances), came back from a 1-4 deficit in the first set against Martincova, who has risen into the Top 100 this season for the first time in her career.

Overall, Azarenka had 19 winners to 17 unforced errors in the clash, while Martincova's seven winners were outpaced by 20 unforced errors.

No.5 seed Elina Svitolina of Ukraine also had a quick trip into the second round as she defeated Canadian qualifier Rebecca Marino, 6-2, 6-3 in just over an hour.

Former Top 40 player Marino was playing the US Open main draw for the first time in 10 years, as her comeback from a nearly five-year break from the tour has hit new heights during this season.

But Svitolina, a US Open semifinalist in 2019 and a title-winner last week in Chicago, was too sturdy on the day for the Canuck. Powerful Marino hit 25 winners to Svitolina's 14, but it was of little consequence as the Ukrainian converted four of her 11 break points while only dropping serve once.

Krejcikova grabs breezy win in main-draw debut

Despite being this year's No.8 seed, reigning Roland Garros champion Barbora Krejcikova had never played a main-draw singles match at the US Open before Monday.

But the Czech had no issues claiming her first victory in New York as she dispatched Australian qualifier Astra Sharma, 6-0, 6-4, needing only an hour and 14 minutes to book her spot in the second round.

Sharma is also having a milestone season in 2021, as the Aussie defeated Ons Jabeur for her first WTA singles title in Charleston this spring. However, Krejcikova won the first eight games of their clash, eventually holding on from there to earn the win. Krejcikova saved both break points she faced in the match.