Japan's defending champion begins her US Open defence with a routine win over Marie Bouzkova

Defending champion Naomi Osaka stretched her Grand Slam win streak to 16 matches on Monday at the US Open while Greek third seed Stefanos Tsitsipas struggled past Andy Murray in five sets. 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.

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. So I'm quite glad to see little kids in the audience and grown ups too. The energy here is unmatched."

Osaka broke Bouzkova in the 10th game of the first set when the Czech netted a backhand, the broke for a 2-0 lead in the second set on the way to victory in 93 minutes. Tsitsipas outlasted Britain's Murray, a three-time Grand Slam champion, by 2-6, 7-6 (9/7), 3-6, 6-3, 6-4 after four hours and 49 minutes in surroundings more like an intense second-week showdown than a curtain-raiser for the fortnight.

Two-time Olympic champion Murray, ranked 112th lost for the first time in 15 first-round US Open matches. Tsitsipas, this year's French Open runner-up, took a long break before the final set, frustrating Murray, who surrendered a break in the opening game. Delay tactics brought a frosty reception at the net after the match. Tsitsipas, who plays Frenchman Adrian Mannarino next, said he followed ATP rules on breaks and medical timeouts, even as Murray questioned the length and timing.

In the second-set tie-breaker, Murray slipped at the net and fell because his sweat-soaked shoes were wet and he didn't have another pair. Murray missed out on two set points and the 23-year-old Greek star won five of the next six points to grab the set and level the match.

"The shoes got so wet that at the end of the set, I was slipping basically and was losing balance. That was my bad. It was an important moment in the match."

Murray broke in the second game of the third set and held out from there, but Tsitsipas took the last two sets to advance.

Two-time Grand Slam champion Simona Halep and Stephens each won to reach the second round.

"You feel the energy. You feel alive on court. Hopefully it will stay like that forever."

Russian second seed Daniil Medvedev defeated Frenchman Richard Gasquet 6-4, 6-3, 6-1 for his 200th career match win and 160th win on hardcourts.

Women's second seed Aryna Sabalenka of Belarus outlasted Serbia's Nina Stojanovic 6-4, 6-7 (4/7), 6-0 while Russian men's fifth seed Andrey Rublev ousted 221st-ranked Ivo Karlovic 6-3, 7-6 (7/3), 6-3.

US Open

Men – First round

Andrey Rublev (RUS x5) bt Ivo Karlovic (CRO) 6-3, 7-6 (7/3), 6-3

Pedro Martínez (ESP) bt James Duckworth (AUS) 4-6, 4-6, 7-6 (9/7), 6-2, 6-2

Frances Tiafoe (USA) bt Christopher Eubanks (USA) 7-6 (10/8), 5-7, 6-3, 6-4

Guido Pella (ARG) bt Filip Krajinovic (SRB x32) 6-7 (2/7), 6-3, 6-2, 6-2

Roberto Bautista Agut (ESP x18) bt Nick Kyrgios (AUS) 6-3, 6-4, 6-0

Emil Ruusuvuori (FIN) bt Kamil Majchrzak (POL) 6-4, 6-2, 3-6, 6-1

Bernabé Zapata (ESP) bt Feliciano Lopez (ESP) 5-7, 7-6 (8/6), 4-6, 6-3, 6-3

Félix Auger-Aliassime (CAN x12) bt Evgeny Donskoy (RUS) 7-6 (7/0), 3-6, 7-6 (7/1), 7-6 (10/8)

Christian Garín (CHI x16) bt Norbert Gombos (SVK) 6-3, 4-6, 6-4, 7-6 (7/4)

Henri Laaksonen (SUI) bt John Millman (AUS) 7-6 (8/6), 7-6 (7/2), 6-1

Dusan Lajovic (SRB) bt Benoît Paire (FRA) 6-3, 7-5, 2-6, 6-4

Peter Gojowczyk (GER) bt Ugo Humbert (FRA x23) 1-6, 6-1, 6-2, 5-7, 6-4

Carlos Alcaraz (ESP) bt Cameron Norrie (GBR x26) 6-4, 6-4, 6-3

Arthur Rinderknech (FRA) bt Miomir Kecmanovic (SRB) 6-7 (10/12), 3-6, 7-5, 6-3, 6-4

Adrian Mannarino (FRA) bt Pierre-Hugues Herbert (FRA) 3-6, 4-6, 6-4, 6-3, 6-3

Stefanos Tsitsipas (GRE x3) bt Andy Murray (GBR) 2-6, 7-6 (9/7), 3-6, 6-3, 6-4

Casper Ruud (NOR x8) bt Yuichi Sugita (JPN) 6-3, 6-2, 6-2

Botic van de Zandschulp (NED) bt Carlos Taberner (ESP) 2-6, 3-6, 6-4, 7-5, 6-3

Facundo Bagnis (ARG) bt Taro Daniel (JPN) 6-3, 6-3, 6-3

Marco Trungelliti (ARG) bt Alejandro Davidovich (ESP x29) 5-7, 6-3, 7-5, 6-7 (3/7), 6-4

Brandon Nakashima (USA) bt John Isner (USA x19) 7-6 (9/7), 7-6 (8/6), 6-3

Alex Molcan (SVK) bt Cem Ilkel (TUR) 4-6, 6-3, 6-1, 6-1

Kevin Anderson (RSA) bt Jiri Vesely (CZE) 7-6 (7/1), 4-6, 3-6, 7-6 (7/5), 7-6 (7/4)

Diego Schwartzman (ARG x11) bt Ricardas Berankis (LTU) 7-5, 6-3, 6-3

Grigor Dimitrov (BUL x15) bt Sam Riffice (USA) 6-1, 7-6 (7/3), 6-3

Alexei Popyrin (AUS) bt Radu Albot (MDA) 6-3, 6-7 (3/7), 6-3, 6-3

Marcos Giron (USA) bt Antoine Hoang (FRA) 6-3, 6-4, 7-5

Daniel Evans (GBR x24) bt Thiago Monteiro (BRA) 6-3, 6-7 (6/8), 6-4, 6-1

Philipp Kohlschreiber (GER) bt Marin Cilic (CRO x30) 6-7 (4/7), 6-7 (3/7), 6-2, 6-1, 2-0, retired

Pablo Andújar (ESP) bt Mikhail Kukushkin (KAZ) 3-6, 4-6, 6-4, 6-4, 6-2

Dominik Koepfer (GER) bt Quentin Halys (FRA) 6-4, 3-6, 4-6, 6-3, 6-4

Daniil Medvedev (RUS x2) bt Richard Gasquet (FRA) 6-4, 6-3, 6-1

Women - 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