Li Na of China hits a return to Simona Halep of Romania during their match at the US Open tennis tournament in New York, Aug 30, 2011. [Photo/Agencies]

* All four women's grand slam winners out of US Open

NEW YORK - The last of the reigning women's grand slam champions was shown the door at the US Open Tuesday when error-prone French Open winner Li Na succumbed to unseeded Romanian teenager Simona Halep 6-2 7-5.

Li sprayed the ball long and wide throughout the one-hour, 34-minute first-round encounter, committing 54 unforced errors on a sun-drenched day at Flushing Meadows.

The 29-year-old Chinese said her May victory on the red clay at Roland Garros seems like a long time ago.

"Before I came to the court, I never think like I was a grand slam champion," she said. "The French Open is like three months (ago) already. It's enough time to forget.

"Now is the hard court season. You have to focus on hard court. You can't only think about what you do on a clay court.

"If you think about clay, you have to think about next year, not this year."

Last year's US Open winner and current Australian Open champion Kim Clijsters did not defend her title because of injury, while Wimbledon winner Petra Kvitova was beaten Monday.

Li has stumbled badly in the Paris aftermath, losing confidence with each early-round setback.

"Before the match, (I) talked to my coach," she said. "I said I didn't have good timing to hit the ball. He tells me everything is perfect, everything is fantastic.

"I say, 'Yes, everything is fantastic, but I always lose first round.' I mean, this is not fantastic. We need to change something."

Li could not rely on the rest of her game against Halep, landing only 61 percent of her first serves and failing to fire an ace. She had only 22 winners in the match.

Simona Halep of Romania hits a return to Li Na of China during their match at the US Open tennis tournament in New York, Aug 30, 2011. [Photo/Agencies]

Halep, who played with an ankle injury she suffered in Toronto earlier this month, called the win "unbelievable."

"It's not easy to play against a grand slam champ because it's very top level," she said. "I had emotion. I was nervous before the match.

"But I wanted just to enjoy the match, to feel the ball good, and to play my best... I am happy that I beat her."

Li called her hardcourt breakdown "a terrible feeling."

"Two years in a row, first round here. First round Indian Wells, Miami," she said, shaking her head. "I mean, normally I like hard court a lot.

"I really wanted to do well after Roland Garros. But it's not easy to do. It's always easy to say, 'I want to do, I would like to do.' But I always lose early.

"Now I've lost all the confidence on the court."