The all-conquering Novak Djokovic found the going even easier than expected at the US Open on Tuesday, as food poisoning hampered the challenge of first-round opponent Conor Niland.
The qualifier from Ireland, ranked 197th in the world, wasn't expected to pose much problem for Djokovic, who has surged to the top of the world rankings with nine titles this season - including two Grand Slams.
But a bout of food poisoning that lingered from Sunday morning had left the 29-year-old Niland physically weakened, and Djokovic needed just 44 minutes to take a 6-0, 5-1 lead before Niland called it a day.
"I felt great on the court, and that's something that's really important for the start of the tournament," Djokovic said of his abbreviated appearance on the Arthur Ashe stadium.
The quick match may prove a boon for Djokovic, who suffered just his second defeat of the season when he retired from the Cincinnati final against Andy Murray this month with a sore shoulder.
"I don't think I'm lacking any time on the court or matches," said Djokovic, who has now won 58 of his 60 matches this year.
"This year has been a very long year. So I really don't mind that I spend less time on the court."
Djokovic was part of a stellar line-up on the Ashe court on Tuesday along with women's world number one Caroline Wozniacki, defending men's champion Rafael Nadal and 13-time Grand Slam champion Serena Williams.
Wozniacki cruised into the second round with a 6-3, 6-1 victory over 125th-ranked Nuria Llagostera Vives.
While the top-seeded Dane is keen to claim a maiden Grand Slam title, she again bristled at suggestions that she needs a major crown to validate her number one status.
"I think we should move on," she said as the questions flared again. "Ask me about something else, something more interesting."
But the fact remains that while Wozniacki has consolidated her spot atop the rankings with half a dozen titles this season - the most recent at New Haven on Saturday - she has flopped in Grand Slams, with a semi-final exit in Australia, a third-round defeat at Roland Garros and a fourth-round loss at Wimbledon.
Since then she suffered early exits at Bastad, Toronto and Cincinnati and dropped her father Piotr as her coach.
"I tried a few things that didn't work out," she said. "But I came back last week and won in New Haven, which was a great feeling.
"I'm number one still and I've just won a tournament, so I'm feeling fine, I'm feeling good."
Fourth-seeded Victoria Azarenka of Belarus also advanced with ease, beating Sweden's Johanna Larsson 6-1, 6-3.
"There are always things that could have been done better, but I think I had a pretty solid start," said Azarenka, who drew the short straw among the top women's seeds when she was put on a path to a possible third-round clash with Serena.
Serena is seeded just 28 here, after a rankings slide due to her nearly year-long absence with a series of health problems.
Serena has nevertheless stamped herself a favorite with two hardcourt victories in the build-up to the Open, and her potential third-round clash with Azarenka was the talk of the draw last week.
Azarenka insisted she wasn't worrying about Serena just yet.
"I'm not interested about that before I go out there," she said. "We'll talk about it later maybe."
Romanian teenager Simona Halep, ranked 53 in the world, stunned French Open women's champion Li Na 6-2, 7-5.
"I really wanted to do well after Roland Garros," said Li, who has struggled since her major breakthrough. "But it's not easy to do. Now I lose all the confidence on the court.
"I was feeling, 'Oh, tennis is just too tough for me.'"
Li's exit - after a second-round ouster at Wimbledon - left the women's field without all three of this year's Grand Slam champions.
Australian Open champion Kim Clijsters, winner of the last two US Open titles, is absent with a stomach muscle injury. Wimbledon champion Petra Kvitova lost on Monday, falling to another Romanian, Alexandra Dulgheru.