Serena Williams' quest for a record-equalling 24th Grand Slam got off the mark as Andy Murray rolled back the years with a vintage comeback at the US Open on Tuesday.
Six-time winner Williams powered past 96th-ranked Kristie Ahn after Murray came from two sets down to win a five-set thriller in his first singles Slam match in 18 months.
The pair both progressed to the second round on day two of a US Open that is unrecognisable from previous tournaments, without spectators and with stringent measures to prevent Covid-19 infections.
Williams defeated Ahn 7-5, 6-3 as she started the latest bid of her protracted pursuit to match Margaret Court's Grand Slam title with a straight-sets win at Flushing Meadows.
The 38-year-old overcame the loss of her first service game in the opening set to advance at a virtually empty Arthur Ashe Stadium, where artwork by black artists is displayed in honour of the Black Lives Matter movement against racial injustice.
"I was really happy with how I just fought for every point no matter how I was playing," said Williams.
It has been more than three years since Williams won her 23rd Grand Slam title at the 2017 Australian Open - when she was already pregnant with daughter Olympia.
She has come close since, reaching four major finals only to come away empty-handed, but should have a better chance this time around with several top players absent because of coronavirus concerns or injury.
World No 1 Ashleigh Barty, the second-ranked Simona Halep and Canadian Bianca Andreescu - who stunned Williams in last year's final - are all absent from the behind-closed-doors tournament.
A title win for Williams would also see her become the most decorated women's player at the US Open in the modern era. She is currently tied with Chris Evert on six.
Murray secured a stunning 4-6, 4-6, 7-6 (7/5), 7-6 (7/4), 6-4 come-from-behind victory in a bruising 4 hr and 39 min encounter against Japan's 49th-ranked Yoshihito Nishioka.
The Scotsman, who has barely played in 2020, said he had learnt a lot about his physical condition and the metal hip he received during surgery last year.
"I've just played a four-and-a-half hour match when I never thought I'd be able to," he told reporters.
"I'm not sitting here with my hip throbbing and aching. I'll be able to sleep fine tonight," Murray added.
Tenth seed Garbine Muguruza, the 2016 French Open champion and 2017 Wimbledon winner, advanced to round two with a 6-4, 6-4 victory over Japan's Nao Havino.
She dedicated the win to compatriot Carla Suarez Navarro, who revealed Tuesday that she had been diagnosed with Hodgkin lymphoma and will require six months of chemotherapy.
"You know, she's such a nice woman, so sweet, so kind, so humble. When these things happen to these good people, I feel, like, so sad about it," said Muguruza.
Also in the women's draw, second seed American Sofia Kenin needed just over an hour to score a 6-2, 6-2 win over unseeded Belgian Yanina Wickmayer at Louis Armstrong Stadium.
And ninth seed Johanna Konta beat compatriot Heather Watson 7-6 (9/7), 6-1 in a tie dubbed the "Battle of Britain."
There was disappointment for 40-year-old Venus Williams though who bowed out in the first round for the first time in her career, losing in straight sets to Karolina Muchova.
Another veteran, Belgium's 37-year-old Kim Clijsters, also fell at the first hurdle.
Clijsters making a comeback for the second time in her career and playing in her first Grand Slam draw since 2012, was beaten in three sets by Ekaterina Alexandrova, losing 3-6, 7-5, 6-1.
In the men's competition, number two seed Dominic Thiem progressed to round two when opponent Jaume Munar retired after the second set at Louis Armstrong Stadium.
Munar abandoned before the start of the third set, with Austria's Thiem leading 7-6 (8/6), 6-3.
Thiem now faces India's Sumit Nagal, who became the first Indian man since 2013 to the reach the second round of a Grand Slam event with a 6-1, 6-3, 3-6, 6-1 win over Bradley Klahn of the United States.
The US Open is taking place in a spectator-free bubble at the US National Tennis Centre in New York.
Players movements are tightly controlled and everyone onsite is being tested regularly to minimise the risk of infection.
Argentina's Guido Pella accused tennis chiefs of operating a double-standard over the handling of French player Benoit Paire's positive Covid-19 case.
Paire was withdrawn on Sunday but several French players who had been in contact with him were allowed to remain in the tournament under enhanced safety protocols.
Pella was excluded from last week's Western & Southern Open, a US Open tune-up, despite testing negative after his trainer contracted the virus.
"I am mad at them because of that, because they change the rules when Benoit tested positive. So I want to know why," he said after being knocked out in the first round.
Results from US Open tennis championship in New York on Tuesay (x-denotes seed):
Men's singles
First round
Matteo Berrettini (ITA x6) bt Go Soeda (JPN) 7-6 (7/5), 6-1, 6-4
Ugo Humbert (FRA) bt Yuichi Sugita (JPN) 6-3, 6-4, 6-3
Emil Ruusuvuori (FIN) bt Aljaz Bedene (SLO) 6-3, 3-6, 6-1, 4-6, 6-1
Casper Ruud (NOR x30) bt Mackenzie McDonald (USA) 4-6, 4-6, 6-4, 6-3, 6-2
Ernesto Escobedo (USA) bt Kamil Majchrzak (POL) 7-6 (7/3), 6-2, 6-3
Salvatore Caruso (ITA) bt James Duckworth (AUS) 4-6, 7-5, 7-5, 6-2
Gregoire Barrere (FRA) bt Taro Daniel (JPN) 6-3, 6-4, 3-6, 6-1
Andrey Rublev (RUS x10) bt Jeremy Chardy (FRA) 6-4, 6-4, 6-3
Grigor Dimitrov (BUL x14) bt Tommy Paul (USA) 6-4, 6-3, 6-1
Marton Fucsovics (HUN) bt Hugo Dellien (BOL) 6-3, 6-3, 6-1
Frances Tiafoe (USA) bt Andreas Seppi (ITA) 4-6, 6-3, 6-4, 7-5
John Millman (AUS) bt Nikoloz Basilashvili (GEO x22) 6-1, 6-4, 6-4
Jeffrey Wolf (USA) bt Guido Pella (ARG x29) 6-2, 0-6, 6-3, 6-3
Roberto Carballes (ESP) bt Feliciano Lopez (ESP) 3-6, 7-6 (7/5), 6-4, 6-3
Christopher O'Connell (AUS) bt Laslo Djere (SRB) 4-6, 6-4, 7-6 (7/2), 6-4
Daniil Medvedev (RUS x3) bt Federico Del Bonis (ARG) 6-1, 6-2, 6-4
Roberto Bautista (ESP x8) bt Tennys Sandgren (USA) 6-4, 6-4, 7-6 (7/3)
Miomir Kecmanovic (SRB) bt Gianluca Mager (ITA) 6-4, 6-4, 6-7 (6/8), 3-6, 6-2
Vasek Pospisil (CAN) bt Philipp Kohlschreiber (GER) 7-6 (7/4), 7-5, 7-6 (7/3)
Milos Raonic (CAN x25) bt Leonardo Mayer (ARG) 6-3, 6-2, 6-3
Alex De Minaur (AUS x21) bt Andrej Martin (SVK) 6-4, 6-3, 7-5
Richard Gasquet (FRA) bt Ivo Karlovic (CRO) 7-6 (7/0), 7-6 (7/4), 6-1
Andrey Kuznetsov (RUS) bt Sam Querrey (USA) 6-4, 7-6 (8/6), 6-2
Karen Khachanov (RUS x11) bt Jannik Sinner (ITA) 3-6, 6-7 (7/9), 6-2, 6-0, 7-6 (7/4)
Felix Auger-Aliassime (CAN x15) bt Thiago Monteiro (BRA) 6-3, 6-7 (7/9), 7-6 (8/6), 7-6 (8/6)
Andy Murray (SCO) bt Yoshihito Nishioka (JPN) 4-6, 4-6, 7-6 (7/5), 7-6 (7/4), 6-4
Corentin Moutet (FRA) bt Jiri Vesely (CZE) 6-4, 6-4, 7-5
Daniel Evans (GBR x23) bt Thiago Wild (BRA) 6-2, 6-1, 7-6 (7/5)
Marin Cilic (CRO x31) bt Denis Kudla (USA) 6-7 (3/7), 3-6, 7-5, 7-5, 6-3
Norbert Gombos (SVK) bt Radu Albot (MDA) 6-4, 6-1, 6-4
Sumit Nagal (IND) bt Bradley Klahn (USA) 6-1, 6-3, 3-6, 6-1
Dominic Thiem (AUT x2) bt Jaume Munar (ESP) 7-6 (8/6), 6-3, 0-0 abandon
Women's singles
First round
Madison Keys (USA x7) bt Timea Babos (HUN) 6-1, 6-1
Aliona Bolsova (ESP) bt Jil Teichmann (SUI) 7-6 (7/3), 6-2
Alize Cornet (FRA) bt Lauren Davis (USA) 6-3, 1-6, 6-0
Ysaline Bonaventure (BEL) bt Zhang Shuai (CHN x25) 4-6, 6-3, 6-2
Donna Vekic (CRO x18) bt Kristyna Pliskova (CZE) 3-6, 7-6 (8/6), 6-4
Patricia Tig (ROU) bt Kurumi Nara (JPN) 6-1, 6-0
Tsvetana Pironkova (BUL) bt Liudmila Samsonova (RUS) 6-2, 6-3
Garbine Muguruza (ESP x10) bt Nao Hibino (JPN) 6-4, 6-4
Maria Sakkari (GRE x15) bt Stefanie Vögele (SUI) 6-3, 3-6, 7-5
Bernarda Pera (USA) bt Zarina Diyas (KAZ) 7-6 (7/4), 6-0
Katrina Scott (USA) bt Natalia Vikhlyantseva (RUS) 7-6 (7/3), 6-2
Amanda Anisimova (USA x22) bt Viktoriya Tomova (BUL) 7-5, 7-5
Sloane Stephens (USA x26) bt Mihaela Buzarnescu (ROU) 6-3, 6-3
Olga Govortsova (BLR) bt Asia Muhammed (USA) 6-1, 6-2
Margarita Gasparyan (RUS) bt Monica Puig (PUR) 6-3, 6-7 (0/7), 6-0
Serena Williams (USA x3) bt Kristie Ahn (USA) 7-5, 6-3
Aryna Sabalenka (BLR x5) bt Oceane Dodin (FRA) 7-6 (7/1), 6-4
Victoria Azarenka (BLR) bt Barbara Haas (AUT) 6-1, 6-2
Sachia Vickery (USA) bt Taylor Townsend (USA) 6-2, 6-4
Iga Swiatek (POL) bt Veronika Kudermetova (RUS x29) 6-3, 6-3
Karolina Muchova (CZE x20) bt Venus Williams (USA) 6-3, 7-5
Anna Kalinskaya (RUS) bt Nina Stojanovic (SRB) 6-4, 6-3
Sorana Cirstea (ROU) bt Christina McHale (USA) 6-4, 7-5
Johanna Konta (GBR x9) bt Heather Watson (GBR) 7-6 (9/7), 6-1
Elise Mertens (BEL x16) bt Laura Siegemund (GER) 6-2, 6-2
Sara Sorribes (ESP) bt Claire Liu (USA) 6-2, 6-4
Caty McNally (USA) bt Viktória Kuzmova (SVK) 6-4, 6-1
Ekaterina Alexandrova (RUS x21) bt Kim Clijsters (BEL) 3-6, 7-5, 6-1
Ons Jabeur (TUN x27) bt Katarzyna Kawa (POL) 6-2, 7-6 (8/6)
Kaia Kanepi (EST) bt Katerina Siniakova (CZE) 6-1, 6-2
Leylah Fernandez (CAN) bt Vera Zvonareva (RUS) 6-4, 7-5
Sofia Kenin (USA x2) bt Yanina Wickmayer (BEL) 6-2, 6-2