The US Open's first round begins on Sunday with defending women's champion Aryna Sabalenka looking to recapture top form, while former men's champion Daniil Medvedev faces a familiar foe whom he has failed to beat in previous meetings.

Sabalenka finally won the US Open last year, after two semi-final exits then loss in the 2023 final. But defending the crown has proven tough for most, with the women's singles tournament producing 10 champions in the last 11 years.

The world number one's quest for a fourth Grand Slam win has also been plagued by disappointment as she lost in the finals of the Australian Open and the French Open this year, before bowing out from the semis in Wimbledon.

"I think it's a lot of pressure, definitely. Just because this place is so big, and it feels bigger than the other slams in some ways," said the 27-year-old, aiming to become the first player to defend the title in a decade.

Sabalenka will look for a quick win over Rebeka Masarova on Sunday, but may be in for a fight as her Swiss opponent forced a tiebreaker in the second set before going down in their first meeting in June.

The Belarusian said she was aware of the odds against her.

"I would love to finish the season with a Grand Slam and world number one. But if this goal is not to be, I'll still think this season has been really amazing," she said.

TOP MEN'S MATCH: DANIIL MEDVEDEV V BENJAMIN BONZI

The US Open has been the Grand Slam of choice for Medvedev, with the three-time finalist winning his only major in New York in 2021.

But the 29-year-old Russian has struggled this year, losing in the first round at the French Open and Wimbledon after a second-round exit from the Australian Open.

The 13th seed faces a tough test in the very first round at Flushing Meadows this year, against Benjamin Bonzi, the same opponent who knocked him out at Wimbledon.

Medvedev has failed to beat the Frenchman in both their meetings, having retired during their first match at Roland Garros in 2017.

"I was surprised by his level," Medvedev said after his loss to Bonzi in June. "Whatever I did on the court, it was not bothering him too much. Everything he did was tough for me to play."

Bonzi, ranked 51st, has never gone beyond the third round in a Grand Slam, but picked up wins over some notable opponents in the last year, including Casper Ruud and Lorenzo Musetti.

PEGULA SEEKS GRAND SLAM GLORY AT HOME

Last year's finalist Jessica Pegula is hoping to win her first major in the state where she was born and believes the New York crowd can help her.

The 31-year-old, who faces Egypt's Mayar Sherif in the first round, said the spectators at the U.S. Open can have an effect unlike any other Grand Slam.

"I think of the crowd kind of taking people and carrying them through in whatever way you kind of embrace them," Pegula said on Friday.

"It's just very electric, rowdy, fun, a little bit chaotic. But I feel like it's just New York kind of in a nutshell."

Pegula has been a crowd favourite at the U.S. Open since her Grand Slam main draw debut at Flushing Meadows in 2015.

"I think you know that if you can play well and find ways to win, you can go deep here and anything can happen," she added.

Medvedev and Sabalenka face tricky tests in US Open first round