Eight players will break new ground at the 2021 US Open by contesting the main draw of a Grand Slam for the first time. Get to know them here at wtatennis.com.

Cristina Bucsa en route to her first WTA main draw victory at Belgrade 2021.

Srdjan Stevanovic/Serbia Ladies Open

Cristina Bucsa (ESP)

Who was the last player to defeat Barbora Krejcikova before she surged into the big time this year? The answer is Cristina Bucsa, who defeated the Czech 6-3, 7-5 in Doha qualifying in February, a week before Roland Garros champion Krejcikova reached her first WTA 1000 final in Dubai.

Bucsa, 23, is the second Moldova-born Spaniard to arrive on tour in swift succession. Like Aliona Bolsova, she was born in Chisinau but has lived in Spain since she was a child, and has been steadily climbing the rankings ladder since making her pro debut in 2013.

Gallery: Welcome to the Tour: All of 2021's WTA debutantes

Her most significant boost came in November 2019, when Bucsa's first ITF W60 title in Nantes lifted her into the Top 200 for the first time. This April, she made her WTA main draw debut in Bogota, and a month later won her first WTA main draw match over Danka Kovinic in Belgrade.

Having fallen in the last round of qualifying at Wimbledon, Bucsa has been ruthless in clearing that hurdle this week, defeating Kateryna Kozlova, Elvina Kalieva and Oceane Dodin without dropping a set. She will open against Cincinnati runner-up Jil Teichmann in the main draw.

Dalma Galfi (HUN)

As a junior, Hungary's Dalma Galfi was predicted for big things. In 2015, she defeated Sofia Kenin to win the US Open girls' title, adding to the Wimbledon girls' doubles trophy which she had won with compatriot Fanny Stollar. That year, she reached World No.1 in juniors and was named the ITF Junior World Champion; the following season, strong ITF results including a runner-up showing at the Tokyo W100 event saw her crack the Top 200 in November 2016. She hit her career high of No.136 in June 2017.

Thereafter, Galfi stalled. "I wouldn't say I had much pressure in the beginning, because I was still kind of a junior, I was young," she told Tennis.com this year. "Then, I began to feel like I was the one putting pressure on myself for the next couple of years, where I knew I could reach this level but just didn't have the mindset for it."

By November 2018, Galfi had fallen out of the Top 350. But 2021 has seen the 23-year-old compile a consistently impressive renaissance. In June, she won her first ITF title in five years at the Denain W25 event, and followed it with a run to the Contrexéville W100 final a month later.

The week after that, Galfi put together a breakthrough showing as a wildcard in her home tournament of Budapest, knocking off Anna Karolina Schmiedlova and Olga Danilovic to reach her first WTA semifinal. This week, back at the site of her finest junior triumph, she cleared the final hurdle of US Open qualifying in impressive fashion, 6-1, 6-3 over Monica Niculescu.

Since June, Galfi has won 17 of her last 22 matches, and will have the chance to extend that against No.30 seed Petra Martic in the first round.

Valentini Grammatikopoulou (GRE)

In 2018, Greek No.1 Maria Sakkari received a €30,000 grant from her government to prepare for the Olympic Games. She chose to share it with her compatriots, Stefanos Tsitsipas - then a rising ATP star who had yet to crack the Top 10 - and Valentini Grammatikopoulou.

"I think we should split it because Valentini needs the money more than I do, because her ranking position is lower," Sakkari explained to reporters that year.

Read more: How Maria Sakkari's generosity embodies the Olympic spirit

The daughter of a street market worker, Grammatikopoulou won her first two ITF titles as a 16-year-old in 2013, made her WTA main draw debut in 2017 after qualifying for Washington, DC and scored her first WTA win at Bogota 2018. But she has suffered from inconsistency since, falling from a career high of No.158 in November 2018 to No.287 this May.

"I traveled two years by myself to all the tournaments," she told itftennis.com in 2019 after being selected as a Grand Slam Development Fund recipient. "When you play against a girl who has a team, mentally you lose. When you do it alone and you lose, you say, 'Maybe it's not your tennis, maybe it's not your life, maybe it's better to quit?'"

Watch: Paolini saves two match points, survives Grammatikopoulou - Lausanne highlights

Help from both the ITF and her friend Sakkari enabled Grammatikopoulou to keep going - and to relocate from the small town of Axioupoli, with its tennis courts made from converted basketball courts, to the Netherlands. This year, it's all paying off. Grammatikopoulou lost a scintillating first-round clash in Lausanne to Jasmine Paolini from match points up, but used that test against a Top 100 player to push on to her 12th ITF title in Telavi, Georgia the following week.

Having lost in Grand Slam qualifying 12 times between 2017 and 2019, on her return to that level this week Grammatikopoulou has had to fight hard to snap that streak. The 24-year-old won each of her matches in three sets over Lucia Bronzetti, Anna Kalinskaya and Liang En-Shuo, saving a match point in the last of those. Her reward is a first-round clash with Anna Blinkova.

Ashlyn Krueger (USA)

Junior World No.26 Ashlyn Krueger, 17, secured a US Open main draw wildcard by winning the USTA Billie Jean King Girls 18s National Championships earlier this month, beating Elvina Kalieva and Reese Brantmeier in the last two rounds. (Both Kalieva and Brantmeier scored impressive wins in qualifying this week.)

Krueger, who hails from Lewisville, Texas, had also served notice of her potential by winning the prestigious Orange Bowl junior event last December, beating Victoria Jimenez Kasintseva en route. This year, she has begun to make an impact at pro level, scoring a career-best win over former World No.35 Olga Govortsova at the Bonita Springs ITF W100 event in May and winning her first WTA qualifying match over Valeria Savinykh in San Jose a month ago.

These results have lifted the teenager to No.647 in the WTA rankings; she is the sixth-highest ranked 2004-born player behind Coco Gauff, Katrina Scott, Robin Montgomery, Linda Noskova and Erika Andreeva.

Rebeka Masarova (ESP)

Back in 2016, all eyes were on Rebeka Masarova. The Basel-born 16-year-old, who had been inspired to play tennis after watching Roger Federer win Wimbledon 2003, defeated Amanda Anisimova to win the Roland Garros girls' title. A month later, Masarova backed it up with a stunning WTA debut, upsetting Jelena Jankovic and Anett Kontaveit en route to the Gstaad semifinals as a No.797-ranked wildcard.

The following January, Masarova would also beat Bianca Andreescu en route to the Australian Open girls' final, which she lost to Marta Kostyuk; other notable victories in her glittering junior career included Iga Swiatek and Dayana Yastremska.

But Masarova has ultimately had to take the scenic route to her Grand Slam debut. At the start of 2018, she switched nationality from Switzerland to Spain, her mother's home country and her training base as a teenager - but knee surgery would sideline her for nine months. She would compete in just 16 tournaments over the next three years, ended 2020 ranked No.717 and began 2021 still stuck in ITF W15 qualifying.

Her surge this season has rocketed her up nearly 500 places. Masarova has won 29 of her last 32 matches since May, including her first two ITF W25 titles in Platja d'Aro and Palma del Río and a first ITF W60 trophy in Vitoria-Gasteiz. Ranked No.231, this week marked her Grand Slam qualifying debut, and the 22-year-old navigated it successfully at her first attempt with wins over Jana Fett, Lara Arruabarrena and Jaqueline Cristian. Masarova will take on Ana Bogdan in the first round of the main draw.

Emma Navarro (USA)

Emma Navarro enjoyed a stellar junior career which peaked at the 2019 Roland Garros girls' event, where she came runner-up in singles to Leylah Fernandez and won the doubles with Chloe Beck. This year, she reminisced to Charleston Magazine about how playing on the Parisian clay was "like playing on silk".

Navarro, 21, is the daughter of Charleston tournament owner Ben Navarro; she made her WTA debut as a wildcard into her home event in 2019, and scored her first WTA main draw wins this year in each of the tournaments held there this April. But she has opted to go the college route instead of turning pro - and has continued to shine as a freshman at the University of Virginia.

This year, Navarro has been named both ACC Freshman of the Year and ITA National Rookie of the Year; she secured a US Open main draw wildcard after defeating Estela Pérez-Somarriba to become the 2021 NCAA singles champion in May. Navarro was the first freshman to win the title since Duke's Mallory Cecil in 2009, and followed in the footsteps of UVA alumna and current World No.28 Danielle Collins, who was a two-time NCAA champion in 2014 and 2016.

Ranked No.331, Navarro will open against fellow American Christina McHale in the first round in Flushing Meadows.

Alycia Parks (USA)

Initially a main draw wildcard alternate, Alycia Parks got her opportunity upgraded after Venus Williams moved into the list of direct entrants (and subsequently withdrew from the tournament). The 20-year-old, born in Atlanta, Georgia but resident in Florida, has been steadily making her way up the rankings over the past year.

Last October, Parks was ranked No.368. A significant boost came after she won the strong ITF W25 title in Orlando, beating Robin Montgomery in the final, and in 2021 Parks has continued to build on her success. She qualified for her first WTA main draw at the Charleston 250 in April, and defeated Grace Min to reach the second round; another WTA main draw victory followed in Lausanne in April, where Parks beat Anna-Lena Friedsam before taking defending champion Fiona Ferro to three sets.

Now ranked No.246, Parks - who has yet to compete in any Grand Slam qualifying events - will get her first taste of the major stage against qualifier Olga Danilovic.

Nuria Párrizas Díaz (ESP)

Taking late-blooming to a new level, Nuria Párrizas Díaz has been one of the most remarkable stories of the year. Last week, the 30-year-old Spaniard became the fourth-oldest player to debut in the Top 100 after winning the Landisville ITF W100 title; and, after falling at the final hurdle in Roland Garros and Wimbledon qualifying this year, she surged into the US Open main draw for the loss of just 15 games in three matches this week.

Párrizas Díaz made her pro debut in July 2006, cracked the Top 500 in May 2012 and won her first ITF $10K title in July 2013. In 2015, she suffered what doctors told her was a career-ending shoulder injury, and did not compete for 14 months. But since returning in September 2016, Párrizas Díaz has been unbothered by it - and this year, she has been reaping the rewards of 15 years of toil.

Read more: Párrizas Díaz claims career-best title at Bastad 125

Her 2021 record so far is a whopping 48-13, including the Bastad WTA 125 title in July as well as five ITF trophies. She made her WTA main draw debut after qualifying for Bogota in April, promptly scoring her first Top 100 victory over Arantxa Rus to reach the quarterfinals. Another WTA quarterfinal followed in Gdynia this July.

The eight oldest players to break the Top 100 for the first time
Tzipora Obziler (ISR) at 33y, 306d
Adriana Villagran (ARG) at 31y, 359d
Tina Mochizuki (USA) at 30y, 138d
Nuria Párrizas Díaz (ESP) at 30y, 32d
Mihaela Buzarnescu (ROU) at 29y, 165d
Julie Ditty (USA) at 28y, 305d
Eva Bes (ESP) at 28y, 183d
Mashona Washington (USA) at 28y, 49d

This year, Párrizas Díaz has been accompanied by new coach and former ATP player Carlos Boluda Purkiss, whom she started dating during last year's Spanish lockdown. "She has always been very alone on the circuit, so I decided to help her," Boluda Purkiss told Punto de Break in February, having retired from his own career to do so.

"It's too early to say if I can be a good coach, but I know that for her I am. I know her perfectly, I know what she thinks, what is good for her and what is bad for her. When you connect with your coach like that, it's the best there is. With a glance we understand each other... it is what I always wanted to have with my coach."

World No.94 Párrizas Díaz's first Grand Slam main draw test will be Varvara Gracheva, with a potential second round looming against compatriot and No.24 seed Paula Badosa.

Wimbledon 2021's Grand Slam debutantes: Raducanu, Burrage
Roland Garros 2021's Grand Slam debutantes: Osorio Serrano, Liang, Gorgodze and more
Australian Open 2021's Grand Slam debutantes: Danilovic, Jones
Roland Garros 2020's Grand Slam debutantes: Tauson, Sherif, Zarazua and more
US Open 2020's Grand Slam debutantes: Gracheva, Baptiste, Montgomery and more
Australian Open 2020's Grand Slam debutantes: Fernandez, Li, Stojanovic and more
US Open 2019's Grand Slam debutantes: Wang Xiyu, Volynets, Bolkvadze
Wimbledon 2019's Grand Slam debutantes: Gauff, McNally, Flink
Roland Garros 2019's Grand Slam debutantes: Rybakina, Samsonova, Juvan and more
Australian Open 2019's Grand Slam debutantes: Swiatek, Kudermetova, Badosa and more
US Open 2018's Grand Slam debutantes: Muchova, Yastremska, Teichmann and more
Wimbledon 2018's Grand Slam debutantes: Ruse, Dart, Lapko and more
Roland Garros 2018's Grand Slam debutantes: Krejcikova, Dolehide, García Pérez and more
Australian Open 2018's Grand Slam debutantes: Kostyuk, Pera, Wang Xinyu and more

Drops, counterdrops & set point saves as Galfi gains first WTA win over Bolsova: Budapest Highlights