NEW YORK -- Defending champion Aryna Sabalenka moved into the second round of the US Open on Sunday after weathering a challenging first set in her first match.
The No. 1-ranked player took down Swiss player Rebeka Masarova 7-5, 6-1, but it wasn't without struggle. Sabalenka went down a break early in the first set, keeping the two neck-and-neck until the defending champion was able to pull away from their 5-5 deadlock.
Sabalenka then dominated the second set, dropping only one game en route to her eventual victory.
"I feel like I didn't start my best in the first games, but then I found my rhythm," she said after the win. "Happy with the level I played today."
She credited the crowd at Arthur Ashe Stadium for helping her make it through that tight first set.
"When I won that set point and you were cheering me up, I had goosebumps while I was sitting," Sabalenka said on the court. "Your support means a lot to me, and thank you so much."
Since the start of 2023, Sabalenka has won 59 major matches to lead all women. She is bidding to become the first woman to successfully defend her US Open title since Serena Williams in 2014. This run of 10 straight US Opens without a back-to-back champion on the women's side is the longest since the tournament eliminated the challenge round in 1912.
The three-time Slam champion has gone through three of this year's four Grand Slams without a title.
Sabalenka will next face Polina Kudermetova, who became the first player to advance at this year's tournament when her opponent Nuria Parrizas Diaz retired after only four games.
Sabalenka defeated Kudermetova in their most recent matchup in Dubai in February.
In other women's singles results Sunday, Janice Tjen took down No. 24 seed Veronika Kudermetova 6-4, 4-6, 6-4 to become the first Indonesian player to win a major match since Angelique Widjaja at Wimbledon in 2003.
"It means a lot," Tjen said. "I feel proud to be able to do this for my country. Hopefully, [my] appearance here will help inspire more ... younger kids to play tennis and also believe they can be here too."
Awaiting Tjen in the second round is Emma Raducanu, who won a match in New York for the first time since she captured the 2021 US Open title, eliminating Ena Shibahara 6-1, 6-2. Raducanu needed just 62 minutes to advance, the fastest major match win of her career.
American Emma Navarro, a US Open semifinalist in 2024, faced a tough opening set against Wang Yafan that lasted 76 minutes before ultimately prevailing 7-6 (9), 6-3 to set up an All-American second-round matchup with Caty McNally.
Other seeded players to advance were McCartney Kessler (32), Leylah Fernandez (31), Jelena Ostapenko (25) and Belinda Bencic (16), coming off a semifinal appearance at Wimbledon.
In the night session, No. 7 seed Jasmine Paolini, fresh off her run to the Cincinnati Open final, eased past Destanee Aiava 6-2, 7-6 (4) on Louis Armstrong. Paolini now has 25 major match wins since the start of last season -- fourth most among women in that span behind Sabalenka (36), Iga Swiatek (32) and Coco Gauff (27).
American Jessica Pegula, last year's runner-up at Flushing Meadows, defeated Mayar Sherif, 6-0, 6-4, in the last match at Arthur Ashe Stadium.
ESPN Research and The Associated Press contributed to this report.