Sept. 1 (UPI) -- Men's and women's top seeds Novak Djokovic and Karolina Pliskova each claimed straight-set wins in their first round matches at the 2020 U.S. Open, while American teen phenom Coco Gauff lost early at the Grand Slam.
Many of the tennis' top players have opted out of the Grand Slam over COVID-19 concerns, including five of the men's Top 15 players . World No. 1 Ashleigh Barty, No. 2 Simona Halep, No. 5 Elina Svitolina, No. 7 Kiki Bertens, No. 8 Belinda Bencic and defending champion Bianca Andreescu are among the top women's players who are not in Queens.
The lone United States-based Grand Slam is being played without fans in attendance due to coronavirus safety precautions.
"The intensity was [still] there," Djokovic told reporters. "I came out and played really well in the first set before I lost my focus in the second set. I got stressed out a couple times and screamed. That's obviously still there, regardless of the empty stadium.
"I bring a lot of intensity and energy, but I try to bounce back."
Djokovic -- a three-time U.S. Open singles champion -- beat Bosnian Damir Dzumhur 6-1, 6-4, 6-1 in a one-hour, 58-minute match. The world No. 1 fired 32 winners and had 29 unforced errors, compared to Dzumhur's 24 winners and 41 errors.
Djokovic advanced to a second-round clash with England's Kyle Edmund.
Osaka -- the 2018 U.S. Open women's singles champion -- beat Doi 6-2, 5-7, 6-2 in 2:03. She had six aces and fired 25 winners in the victory compared to Doi's one ace and 17 winners. Osaka will battle Italy's Camila Giorgi in the second round.
"I wanted to stay calm coming into this tournament," Osaka said. "It's tough to play players when you feel like they are going to raise their level. You feel like they have nothing to lose."
The world No. 9 wore a black mask that read "Brionna Taylor" before and after the match. Taylor -- a Black woman -- was fatally shot by police in March in Louisville, Ky. Last week, Osaka pulled out of her semifinal match at the Western & Southern Open to join a sportswide protest sparked by the recent police-involved shooting of Jacob Blake.
A full day of Western & Southern Open matches was later postponed due to the protests before Osaka resumed play at that tournament, which also was played in Queens.
Osaka said she has a total of seven masks, which feature names of more people who have been impacted by police-involved violence, to wear at the U.S. Open. Osaka would appear in seven matches if she makes it to the women's singles final.
"It's quite sad that seven masks isn't enough for the amount of matches [at U.S. Open]," Osaka said. "Hopefully I'll get to the final and you can see all of them."
World No. 45 Anastasija Sevastova beat Coco -- No. 51 -- 6-3, 5-7, 6-4 to advance to a second-round clash with Marta Kostyuk. Pliskova took out Ukrainian Anhelina Kalinina 6-0, 6-4 to advance to the second round.
Petra Kvitova, Petra Martic, Angelique Kerber and Americans Jessica Pegula, Madison Brengle, Shelby Rogers, Alison Riske, Ann Li, Jennifer Brady and Catherine Bellis were also among the women's players to advance.
Alexander Zverev, Borna Coric, Stefanos Tsitsipas, David Goffin, Gilles Simon, Denis Shapovalov and Djokovic were among the top men's players to advance. American's Jack Sock, Michael Mmoh, Mitchell Krueger, Steve Johnson, Taylor Fritz, Marcos Giron, Maxime Cressy and Brandon Nakashima also won their first-round affairs.
Tuesday's top matches
Men's singles - Estimated in EDT
Andy Murray vs. Yoshihito Nishioka at noon
Marin Cilic vs. Denis Kudla at 12:15 p.m.
Andrey Rublev vs. Jeremy Chardy at 12:15 p.m.
Dominic Thiem vs. Jaume Munar at 12:15 p.m.
Roberto Bautista Agut vs. Tennys Sandgren at 2:15 p.m.
Milos Raonic vs. Leonardo Mayer at 2:15 p.m.
Matteo Berrettini vs. Go Soeda at 5:30 p.m.
Grigor Dimitrov vs. Tommy Paul at 6:15 p.m.
Daniil Medvedev vs. Federico Delbonis at 8:15 p.m.
Women's singles - Estimated in EDT
Amanda Anisimova vs. Viktoriya Tomova at 11 a.m.
Garbine Muguruza vs. Nao Hibino at 11 a.m.
Monica Puig vs. Margarita Gasparyan at 11 a.m.
Johanna Konta vs. Heather Watson at 12:15 p.m.
Serena Williams vs. Kristie Ahn at 2 p.m.
Sloane Stephens vs. Mihaela Buzarnescu at 4:15 p.m.
Aryna Sabalenka vs. Oceane Dodin at 4:15 p.m.
Madison Keys vs. Timea Babos at 5 p.m.
Maria Sakkari vs. Stefanie Voegele at 6:15 p.m.
Venus Williams vs. Karolina Muchova at 7 p.m.