NEW YORK -- Daniil Medvedev had an easy start to his US Open title defense, beating Stefan Kozlov 6-2, 6-4, 6-0 on Monday.
On the same Arthur Ashe Stadium court where that night Serena Williams was set to begin what could be the final tournament of her career, the top-seeded Medvedev looked just as strong as he did in sweeping past Novak Djokovic in last year's final for his first major title.
Medvedev advanced to face Arthur Rinderknech of France. The Russian player is trying to become the first repeat champion at the US Open since Roger Federer won five straight from 2004 to '08.
"I need to be at my best on Wednesday and I'm going to try to make it," Medvedev said.
Andy Murray was another early winner, 10 years after winning the first of his three Grand Slam titles in Flushing Meadows. He had one of the first upsets of the tournament by beating No. 24 seed Francisco Cerundolo of Argentina 7-5, 6-3, 6-3.
"It seems like a long time ago," Murray said of his victory over Djokovic in 2012. "A lot's happened since then in my career."
Djokovic couldn't travel to the tournament this year because he isn't vaccinated against COVID-19.
Leading 3-0 in the third set, Medvedev told the chair umpire he wanted a bag of ice so he could put it on his head.
"Pretty hot and humid here," Medvedev said after the match.
No. 29 seed Tommy Paul overcame the heat to outlast Bernabe Zapata Miralles 4-6, 6-3, 2-6, 6-0, 7-5 in 3 hours, 10 minutes. Fellow American Sebastian Korda also got his first win at his home Slam, beating Facundo Bagnis in four sets.
Another American player advanced in an upset, with J.J. Wolf ousting No. 16 seed Roberto Bautista Agut in straight sets.
Yibing Wu, meanwhile, became the first Chinese man to win a US Open match in the professional era when he upset No. 31 seed Nikoloz Basilashvili 6-3, 6-4, 6-0. He had played his way into the field through the qualifying tournament, joining countryman and fellow qualifier Zhizhen Zhang as the first Chinese men in the US Open main draw since the open era began in 1968. Zhang lost to Tim Van Rijthoven on Monday in five sets.
The Associated Press contributed to this report.