Venus Williams and Kim Clijsters bowed out of the US Open at the first hurdle on Tuesday as seeded players dominated the women's draw for a second straight day.
Hours after younger sister Serena had battled into the second round, Venus, 40, was back in the spotlight in what was an incredible 22nd US Open appearance.
But Williams, who reached the final of the US Open on her debut at the tournament in 1997, was beaten in the first round for the first time in her glittering career by Karolina Muchova of the Czech Republic.
Muchova, the 20th seed, had too much poise for Williams en route to a 6-3, 7-5 win.
While Williams knows that time is running out on her career at the top level - she has not gone further than the third round at a Slam event since 2017 - she insisted afterwards that she plans to continue playing, starting with this month's French Open at Roland Garros.
"I love this game," Williams said. "I'm good at what I do. It's easy to stay motivated and excited about doing something so amazing. Not many people get to do this.
"But I look forward to a few days off. It's been a lot of work. Looking forward to just having a little bit of a rest before the clay courts."
Belgium's Clijsters meanwhile, making the second comeback of her career and her first appearance at a Grand Slam since 2012, raised hopes of an upset after taking the first set of her match with Russia's Ekaterina Alexandrova.
The 37-year-old three-time US Open champion ran out of steam though as Alexandrova, seeded 21, completed a 3-6, 7-5, 6-1 win.
This year's women's field in New York is more open than ever with world number one Ashleigh Barty, the second-ranked Simona Halep and defending champion Bianca Andreescu all electing to skip the tournament.
One of the leading contenders for the title, second seed Sofia Kenin of the United States, got off the mark with a 6-2, 6-2 win over unseeded Yanina Wickmayer of Belgium.
The 21-year-old, who won an emotional maiden Grand Slam title at this year's Australian Open, later revealed she had cried to herself before the match in order to alleviate stress.
"Crying. That's what I did. I mean, I had to let it out," Kenin said. "It's fine. It worked."
Kenin will play Canada's Leylah Fernandez in the second round. Fernandez opened her campaign with a 6-4, 7-5, win over Vera Zvonareva on Tuesday.
Ninth seed Jo Konta meanwhile won the 'Battle of Britain' against compatriot Heather Watson, winning 7-6 (9/7), 6-1.
"There's always going to be rivalry between compatriots," Konta said. "It's always going to be that extra stressful.
"There's always going to be an element of people having more judgments and more of an opinion on the outside at home on a match like today," added Konta, who will play Romania's Sorana Cirstea in the second 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