Defending champion Naomi Osaka stretched her Grand Slam win streak to 16 matches on Monday at the US Open while two-time Grand Slam champion Simona Halep, battling back from injury, advanced to the second round.

Osaka, seeking her third US Open crown in four years, defeated 87th-ranked Czech Marie Bouzkova 6-4, 6-1 at a packed Arthur Ashe Stadium to book a second-round matchup with Serbian qualifier Olga Danilovic.

“It feels kind of crazy to play in front of everyone again,” Osaka said. “I feel really comfortable here. I’m just glad I won.”

Osaka beat Bouzkova in their only prior meeting in the first round of this year’s Australian Open on the way to her fourth Grand Slam title.

The 23-year-old Japanese star could become the first back-to-back US Open women’s champion since Serena Williams, out this year with a torn hamstring, won her third in a row in 2014. Osaka’s major win streak includes her most recent US and Australian Open wins and a first-round win at this year’s French Open before withdrawing over mental health issues.

Osaka, who lit the cauldron at the Tokyo Olympics, gave an Olympic pin to a young girl in the same venue where she won last year’s title when fans were banned due to Covid-19.

“It felt quite lonely for me,” she said. “So I’m quite glad to see little kids in the audience and grown ups too. The energy here is unmatched.”

Osaka saved a break point in the ninth game on a service winner and captured the first set by breaking Bouzkova in the 10th game when the Czech netted a backhand. In the second set, Osaka broke for a 2-0 lead, then saved three break points with winners and held in an eight-minute third game on the way to victory in 93 minutes.

Halep, seeded 12th after dropping out of the Top 10 due to injury, defeated Italy’s Camila Giorgi 6-4, 7-6 (7/3) to book a second-round match against Slovakian lucky loser Kristina Kucova, who ousted American Ann Li 7-5, 6-1.

The 29-year-old Romanian, the 2018 French Open and 2019 Wimbledon champion, tore a left calf muscle at the Italian Open, missed the French Open and Wimbledon, then suffered a right thigh injury at Cincinnati, but made a solid New York start.

Halep fired six aces and won 83% of her first serve points, hitting 14 winners against 16 unforced errors while taking advantage of 31 unforced errors by Giorgi.

Spectators had to show proof of vaccination to attend but they brought energy back to Ashe.

“Playing without fans here was brutal,” 2017 US Open winner Sloane Stephens said. “Having these fans out and the energy, the atmosphere, it brings a lot back to tennis.” The former champion beat Madison Keys 6-3, 1-6, 7-6 (9/7) in a rematch of the 2017 final.

Women’s second seed Aryna Sabalenka of Belarus outlasted Serbia’s Nina Stojanovic 6-4, 6-7 (4/7), 6-0 to advance.

Results

First round

Elina Svitolina (UKR x5) bt Rebecca Marino (CAN) 6-2, 6-3

Rebeka Masarova (ESP) bt Ana Bogdan (ROM) 6-7 (9/11), 7-6 (7/2), 7-6 (11/9)

Markéta Vondroušová (CZE) bt Gabriela Ruse (ROM) 7-5, 6-0

Darya Kasatkina (RUS x25) bt Tsvetana Pironkova (BUL) 6-2, 6-1

Elena Rybakina (KAZ x19) bt Aliaksandra Sasnovich (BLR) 6-2, 6-3

Caroline Garcia (FRA) bt Harriet Dart (GBR) 6-7 (6/8), 6-4, 6-2

Kristína Kucová (SVK) bt Ann Li (USA) 7-5, 6-1

Simona Halep (ROM x12) bt Camila Giorgi (ITA) 6-4, 7-6 (7/3)

Angelique Kerber (GER x16) bt Dayana Yastremska (UKR) 3-6, 6-4, 7-6 (7/3)

Anhelina Kalinina (UKR) bt Mayar Sherif (EGY) 4-6, 6-1, 6-1

Sloane Stephens (USA) bt Madison Keys (USA) 6-3, 1-6, 7-6 (9/7)

Cori Gauff (USA x21) bt Magda Linette (POL) 5-7, 6-3, 6-4

Kaia Kanepi (EST) bt Yulia Putintseva (KAZ x31) 2-6, 7-6 (7/4), 6-2

Leylah Fernandez (CAN) bt Ana Konjuh (CRO) 7-6 (7/3), 6-2

Olga Danilovic (SRB) bt Alycia Parks (USA) 6-3, 7-5

Naomi Osaka (JPN x3) bt Marie Bouzková (CZE) 6-4, 6-1

Barbora Krejcíková (CZE x8) bt Astra Sharma (AUS) 6-0, 6-4

Christina McHale (USA) bt Emma Navarro (USA) 6-1, 7-6 (7/5)

Kamilla Rakhimova (RUS) bt Kristina Mladenovic (FRA) 2-6, 6-2, 6-3

Ekaterina Alexandrova (RUS x32) bt Sara Errani (ITA) 6-3, 6-2

Victoria Azarenka (BLR x18) bt Tereza Martincova (CZE) 6-4, 6-0

Jasmine Paolini (ITA) bt Yaroslava Shvedova (KAZ) 6-3, 6-4

Andrea Petkovic (GER) bt Irina Begu (ROM) 6-2, 7-6 (7/3)

Garbiñe Muguruza (ESP x9) bt Donna Vekic (CRO) 7-6 (7/4), 7-6 (7/5)

Elise Mertens (BEL x15) bt Rebecca Peterson (SWE) 3-6, 7-6 (7/5), 7-6 (7/5)

Valentini Grammatikopoulou (GRE) bt Anna Blinkova (RUS) 6-3, 6-2

María Camila Osorio (COL) bt Ivana Jorovic (SRB) 6-2, 6-2

Ons Jabeur (TUN x20) bt Alize Cornet (FRA) 7-5, 7-5

Danielle Collins (USA x26) bt Carla Suárez (ESP) 6-2, 6-4

Kaja Juvan (SLO) bt Heather Watson (GBR) 6-1, 6-4

Tamara Zidanšek (SLO) bt Bernarda Pera (USA) 6-4, 7-6 (7/4)

Aryna Sabalenka (BLR x2) bt Nina Stojanovic (SRB) 6-4, 6-7 (4/7), 6-0

With AFP Inputs