Serena Williams and Rafael Nadal are safely through their first round matches at the US Open in Flushing Meadows, New York, while Ireland's Conor Niland lost to Novak Djokovic.
Williams, less than a month away from turning 30 and in the early stages of a comeback after surviving a life-threatening lung disorder, has been installed as the favourite to win the tournament.
In the last match of Tuesday's night session, the American sent an ominous warning to her rivals when she began her campaign with a 6-1 6-1 win over Serbia's Bojana Jovanovski.
Williams left this competition in disgrace two years ago after a foul mouthed tirade on an official that earned her a hefty fine and a two-year probation, which ends after this tournament.
But the American was on her best behaviour against Jovanovski, racing to victory in less than an hour then sweet-talking the Arthur Ashe Stadium crowd.
"I'm so happy to be here, I didn't think I would make it," she said in an on-court interview.
Nadal began his title defense with a straight sets win over Andrey Golubev of Kazakhstan. The Spaniard won 6-3 7-6 7-5 but it was a performance that raised as many questions as answers.
Last year, Nadal completed his personal grand slam after working tirelessly on his serve, turning a shot that had been a weakness into a weapon. His serve was broken just five times in the seven matches he played last year.
Against Golubev, ranked 98th in the world, his serve was broken six times.
"It's a positive start," Nadal said. "It was unbelievable that I won straight sets, but it is still a victory in straight sets."
Caroline Wozniacki, the women's world number one, provided a glimpse of the ruthless streak her critics have accused her of lacking, demolishing unseeded Spaniard Nuria Llagostera Vives 6-3 6-1.
The Dane, who has been in the headlines as much for her relationship with golfer Rory McIlroy as her performances on court, smashed 22 winners in a lopsided victory that took just 80 minutes.
It was as impressive a start to the tournament as anyone has made so far but Wozniacki was forced to defend herself, and by extension the women's game, because she has still not won a grand slam title.
"They can say what they want," she snarled. "I've won a lot of tournaments. I'm number one in the world."
Li Na is one of the most marketable players in the game since becoming the first Chinese to win a grand slam singles crown but has struggled since, and joined the list of big casualties at the tournament when she fell 6-2 7-5 to unseeded Romanian Simona Halep.
