Djokovic ruthless, Li Na shocked

Roger Federer and Rafa Nadal are seemingly not the only ones sick of the sight of Novak Djokovic and his domination of men's tennis. At the US Open on Tuesday, Ireland's Conor Niland threw up then gave up during his first-round match with the world number one.

- Sania loses in first round

Perhaps the only thing in professional tennis looking more under the weather right now is the state of the women's game. After just two days at Flushing Meadows, not one reigning grand slam singles champion was left in the draw.

Kim Clijsters, who won the US Open last year and the Australian Open earlier this year, did not defend her title because of a stomach muscle problem. On Monday, the Wimbledon champion Petra Kvitova made an inglorious early exit. And Tuesday, she was joined by China's Li Na, the French Open champion.

It is little wonder Serena Williams, less than a month away from turning 30 and in the early stages of a comeback after surviving a life-threatening lung clot, has been installed as the favourite to win the last grand slam of the year. The American was due to play her opening match Tuesday night.

Niland lasted only 44 minutes before he tossed in the towel against Djokovic. He was trailing 6-0, 5-1 and already looking as green as the fluffy balls he was frantically trying to retrieve.

The first Irishman to play at the US Open, he did at least have a valid excuse. He was suffering food poisoning after eating a meal of pork and salad at a fancy Manhattan restaurant.

"I thought I could bluff my way through but you can't do that against the number one in the world, I just found out," Niland said.

It was not a fair contest anyway. Djokovic, his appetite for more Gand Slam titles still driving him, was in a ruthless mood and showing little charity to his ailing opponent.

He showed no ill effects of the shoulder injury that forced him to quit last week's Cincinnati final against Andy Murray but was glad to get an early mark on a hot and sunny afternoon at Flushing Meadows.

'ANY SURFACE'

"I really don't mind that I spend less time on the court," Djokovic said.

The Serbian has lost just two matches this year, claiming the Wimbledon and Australian Open titles along the way, but his intentions for the next two weeks are clear and his main rivals have been put on notice.

"Now, more than ever, I know that I can actually perform equally well on any surface," he said.

Nadal began his title defence with a straight sets win over Andrey Golubev of Kazakhstan on Tuesday. 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.

"I was a little bit lucky to win today in straight sets," Nadal said. "He was a very difficult player to play. He played very fast."

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."

"There are a lot of things to my game I can still improve, but everyone can. I'm on the right track."

Sixth-seeded Li joined fifth seed Kvitova as the first big casualties of the tournament when she fell 6-2, 7-5 to unseeded Romanian Simona Halep.

Li became one of the most marketable players in the game when she became the first Chinese to win a Grand Slam singles crown but she has struggled since.

"I really wanted to do well after Roland Garros," Li said.

"(But) Now I lose all the confidence on the court. I was feeling, 'Oh, tennis (is) just too tough for me."