Aug. 31 (UPI) -- Top-seeded Novak Djokovic began his historic bid for the first calendar-year Grand Slam in men's tennis since 1969 with a first-round victory over Danish qualifier Holger Rune at the U.S. Open on Tuesday in Flushing, N.Y.
Djokovic, also seeking a record-breaking 21st major singles championship, quickly regained control after dropping the second set and went on to earn a 6-1, 6-7 (5), 6-2, 6-1 win over Rune in Arthur Ashe Stadium to reach the second round.
"It wasn't the best of my performances," Djokovic said after the match. "But at the same time, [Rune] played well in the second set when it mattered."
In other men's action at the U.S. Open, Pablo Carreno Busta -- who toppled Djokovic for the bronze medal at the Summer Games in Tokyo earlier this month -- suffered an upset loss to Maxime Cressy in the opening round.
The ninth-seeded Carreno Busta was eliminated 5-7, 4-6, 6-1, 6-4, 7-6 (7) by Cressy, a Paris-born American who is ranked 151st. No. 27 seed David Goffin also fell in the first round at the hands of unseeded American Mackenzie McDonald in straight sets.
No. 22 seed Reilly Opelka swept past Soon Woo Kwon to reach the second round, while unseeded Lloyd Harris knocked off 25th-seeded Karen Khachanov in five sets. No. 6 seed Matteo Berrettini, No. 7 Denis Shapovalov, No. 10 Hubert Hurkacz and No. 13 Jannik Sinner also advanced.
On the women's side of the tournament, top-seeded Ash Barty held off 2010 runner-up Vera Zvonareva 6-1, 7-6 (7) to reach the second round.
Barty won at Wimbledon earlier this year for her second major title and returns to New York after staying in Australia last year when the U.S. Open was held without fans due to the COVID-19 pandemic.
"I was disappointed not to be able to come and play last year, but I think playing here this year with fans makes it all the better," Barty said.
Also Tuesday, fourth-seeded Karolina Pliskova -- the 2016 runner-up at the U.S. Open -- defeated American teenager Caty McNally 6-3, 6-4. No. 11 seed Belinda Bencic beat Arantxa Rus 6-4, 6-4, and No. 17 Maria Sakkari eliminated Marta Kostyuk 6-4, 6-3.