New York - Reigning US Open champion Naomi Osaka confronted severe nerves as she survived a rocky start to her title defense Tuesday but an ailing Stefanos Tsitsipas slumped to a four-set defeat by Andrey Rublev in the opening round.
Osaka suffered a first-round exit last month at Wimbledon and the Japanese star struggled to put away Russia's Anna Blinkova in her opener at Arthur Ashe Stadium before prevailing 6-4, 6-7 (5/7), 6-2 in two hours and 28 minutes.
"I have a lot of really good memories here because I grew up in this area. I don't think I've ever been this nervous in my life," Osaka said.
"You want to do well after you did well last year. I definitely didn't want to lose in the third set."
The top seed goes on to face Poland's Magda Linette, who captured her maiden WTA title in the Bronx last week.
Osaka must retain her Flushing Meadows crown to have a chance of remaining world number one and was tested extensively by 2015 Wimbledon junior finalist Blinkova, who saved a match point as Osaka served for victory in the second set to force a decider.
World number 84 Blinkova raced 4-1 ahead in the first set but Osaka, sporting a black brace on the left knee that prompted her to retire in Cincinnati 10 days ago, steadied herself and reeled off five straight games.
Blinkova blew three set points as Osaka served at 4-5 in the second but capitalized at the fifth attempt, edging the tie-break as Osaka cracked with the finish in sight.
The Japanese crucially snuffed out a pair of break chances early in the third before knifing through the Blinkova serve the following game with a thumping inside-out forehand to take a 3-1 lead.
A lengthy hold consolidated Osaka's advantage and the 21-year-old finally closed out a battling win to avoid a repeat of her Wimbledon misery.
"It's kind of just a game so I have to remember that," Osaka said. "It helps me a lot because I learn from the tougher matches. It helps me to prepare."
Greek eighth seed Tsitsipas struggled with cramps and became the biggest casualty in the men's draw as he was dumped out by 2017 quarter-finalist and Next Gen rival Rublev 6-4, 6-7 (5/7), 7-6 (9/7), 7-5 in a gruelling four-hour slog.
Russia's Rublev kept the momentum rolling after his win over Roger Federer at the Cincinnati Masters, and will play France's Gilles Simon in round two.
"It was tough for both of us. It was tough conditions and we both played an amazing match," said Rublev.
"I was tired and he started to cramp. I tried to show I was not cramping."
"A win like this means a lot to me," he added. "We're going to play many, many more times. This match is the beginning, it is very special."
It was a second successive Grand Slam first-round exit for Tsitsipas, while Spanish 10th seed Roberto Bautista Agut succumbed in five sets to Mikhail Kukushkin of Kazakhstan.
Marin Cilic, the 2014 champion, advanced in straight sets over Slovakia's Martin Klizan.
Women's sixth seed Petra Kvitova knocked off Czech qualifier Denisa Allertova 6-2, 6-4 and was joined in the second round by seventh-seeded Kiki Bertens and Canadian teenager Bianca Andreescu, who is making her US Open main draw debut.
Rafael Nadal launches his bid for a fourth US Open crown in the night session on Ashe against Australia's John Millman, the conqueror of Federer in the last 16 here a year ago.
The Spaniard owns 18 Grand Slam titles, two shy of Federer's all-time record. Along with defending champion Novak Djokovic the "Big Three" have combined to win the past 11 majors and are again strong favorites.
Simona Halep opens against American Nicole Gibbs in Louis Armstrong Stadium, where Australian firebrand Nick Kyrgios has been assigned the "graveyard shift" as the last match on that court against Steve Johnson.
Sloane Stephens, the 2017 US Open winner, takes on Russian qualifier Anna Kalinskaya in round one, with 15-year-old Wimbledon sensation Coco Gauff making her New York debut against Russia's 76th-ranked Anastasia Potapova.
Results from Tuesday's second day of the US Open tennis championships: (x denotes seed):
Andrey Rublev (RUS) bt Stefanos Tsitsipas (GRE x8) 6-4, 6-7 (5/7), 7-6 (9/7), 7-5
Gilles Simon (FRA) bt Bjorn Fratangelo (USA) 5-7, 7-5, 7-5, 7-5
Matteo Berrettini (ITA x24) bt Richard Gasquet (FRA) 6-4, 6-3, 2-6, 6-2
Jordan Thompson (AUS) bt Joao Sousa (POR) 6-3, 6-2, 6-4
Alexei Popyrin (AUS) bt Federico Del Bonis (ARG) 6-1, 7-5, 7-6 (7/5)
Mikhail Kukushkin (KAZ) bt Roberto Bautista Agut (ESP x10) 3-6, 6-1, 6-4, 3-6, 6-3
Gael Monfils (FRA x13) bt Albert Ramos (ESP) 7-6 (7/2), 6-4, 6-3
Marius Copil (ROU) bt Ugo Humbert (FRA) 6-3, 5-7, 7-6 (13/11), 4-6, 6-1
Denis Shapovalov (CAN) bt Felix Auger-Aliassime (CAN x18) 6-1, 6-1, 6-4
Pablo Andujar (ESP) bt Kyle Edmund (GBR x30) 3-6, 7-6 (7/1), 7-5, 5-7, 6-2
Lorenzo Sonego (ITA) bt Marcel Granollers (ESP) 6-3, 6-4, 6-4
Alexander Bublik (KAZ) bt Santiago Giraldo (COL) 2-6, 6-0, 7-5, 3-6, 6-4
Thomas Fabbiano (ITA) bt Dominic Thiem (AUT x4) 6-4, 3-6, 6-3, 6-2
Alexander Zverev (GER x6) bt Radu Albot (MDA) 6-1, 6-3, 3-6, 4-6, 6-2
Frances Tiafoe (USA) bt Ivo Karlovic (CRO) 6-2, 6-3, 1-2, retired
Aljaz Bedene (SLO) bt Jozef Kovalík (SVK) 6-3, 6-4, 7-5
Benoît Paire (FRA x29) bt Brayden Schnur (CAN) 6-2, 6-4, 6-4
Diego Schwartzman (ARG x20) bt Robin Haase (NED) 6-3, 7-6 (8/6), 6-0
Egor Gerasimov (BLR) bt Lloyd Harris (RSA) 7-5, 7-6 (7/5), 7-6 (7/3)
Tennys Sandgren (USA) bt Jo-Wilfried Tsonga (FRA) 1-6, 6-7 (2/7), 6-4, 7-6 (7/5), 7-5
Vasek Pospisil (CAN) bt Karen Khachanov (RUS x9) 4-6, 7-5, 7-5, 4-6, 6-3
John Isner (USA x14) bt Guillermo Garcia-Lopez (ESP) 6-3, 6-4, 6-4
Jan-Lennard Struff (GER) bt Casper Ruud (NOR) 6-4, 6-4, 6-2
Cedrik-Marcel Stebe (GER) bt Filip Krajinovic (SRB) 6-3, 4-6, 6-4, 7-6 (8/6)
Marin Cilic (CRO x22) bt Martin Klizan (SVK) 6-3, 6-2, 7-6 (8/6)
Fernando Verdasco (ESP x32) bt Tobias Kamke (GER) 6-3, 3-6, 6-1, 6-2
Chung Hyeon (KOR) bt Ernesto Escobedo (USA) 3-6, 6-4, 6-7 (5/7), 6-4, 6-2
Thanasi Kokkinakis (AUS) bt Ilya Ivashka (BLR) 6-3, 7-6 (10/8), 6-7 (4/7), 6-2
Rafael Nadal (ESP x2) bt John Millman (AUS) 6-3, 6-2, 6-2
Antoine Hoang (FRA) bt Leonardo Mayer (ARG) 3-6, 6-2, 6-7 (6/8), 6-1, 6-3
Henri Laaksonen (SUI) bt Marco Cecchinato (ITA) 7-6 (7/3), 7-6 (8/6), 2-6, 3-6, 7-6 (7/2)
Nick Kyrgios (AUS x28) bt Steve Johnson (USA) 6-3, 7-6 (7/1), 6-4
Naomi Osaka (JPN x1) bt Anna Blinkova (RUS) 6-4, 6-7 (5/7), 6-2
Magda Linette (POL) bt Astra Sharma (AUS) 6-3, 6-4
Cori Gauff (USA) bt Anastasia Potapova (RUS) 3-6, 6-2, 6-4
Timea Babos (HUN) bt Carla Suarez Navarro (ESP x28) 6-2, 0-0, retired
Anett Kontaveit (EST x21) bt Sara Sorribes (ESP) 6-1, 6-1
Ajla Tomljanovic (AUS) bt Marie Bouzková (CZE) 1-6, 7-5, 6-1
Alize Cornet (FRA) bt Jessica Pegula (USA) 6-2, 6-3
Belinda Bencic (SUI x13) bt Mandy Minella (LUX) 6-3, 6-2
Kaia Kanepi (EST) bt Tatjana Maria (GER) 5-7, 7-6 (7/4), 6-3
Julia Görges (GER x26) bt Natalia Vikhlyantseva (RUS) 1-6, 6-1, 7-6 (7/1)
Francesca Di Lorenzo (USA) bt Veronika Kudermetova (RUS) 7-6 (7/4), 6-2
Anastasia Pavlyuchenkova (RUS) bt Pauline Parmentier (FRA) 6-1, 7-6 (7/2)
Kiki Bertens (NED x7) bt Paula Badosa (ESP) 6-4, 6-2
Simona Halep (ROU x4) bt Nicole Gibbs (USA) 6-3, 3-6, 6-2
Taylor Townsend (USA) bt Kateryna Kozlova (UKR) 3-6, 6-3, 6-2
Sorana Cirstea (ROU) bt Katerina Siniakova (CZE) 7-5, 6-2
Aliona Bolsova (ESP) bt Barbora Strycova (CZE x31) 6-3, 0-6, 6-1
Caroline Wozniacki (DEN x19) bt Wang Yafan (CHN) 1-6, 7-5, 6-3
Danielle Collins (USA) bt Polona Hercog (SLO) 6-3, 4-6, 6-4
Kirsten Flipkens (BEL) bt Wang Xiyu (CHN) 3-6, 6-2, 6-2
Bianca Andreescu (CAN x15) bt Katie Volynets (USA) 6-2, 6-4
Kristie Ahn (USA) bt Svetlana Kuznetsova (RUS) 7-5, 6-2
Jelena Ostapenko (LAT) bt Aleksandra Krunic (SRB) 6-3, 7-6 (9/7)
Alison Riske (USA) bt Garbine Muguruza (ESP x24) 2-6, 6-1, 6-3
Elise Mertens (BEL x25) bt Jil Teichmann (SUI) 6-2, 6-2
Kristyna Pliskova (CZE) bt Diane Parry (FRA) 6-4, 6-3
Andrea Petkovic (GER) bt Mihaela Buzarnescu (ROU) 6-3, 6-4
Petra Kvitova (CZE x6) bt Denisa Allertova (CZE) 6-2, 6-4
Donna Vekic (CRO x23) bt Richel Hogenkamp (NED) 7-6 (7/4), 6-3
Yulia Putintseva (KAZ) bt Madison Brengle (USA) 6-3, 6-3
Aryna Sabalenka (BLR x9) bt Victoria Azarenka (BLR) 3-6, 6-3, 6-4
Anna Kalinskaya (RUS) bt Sloane Stephens (USA x11) 6-3, 6-4