Czech Republic's Petra Kvitova returns the ball to Russia's Vera Zvonareva during their semi-final match at the Pan Pacific Open tennis tournament in Tokyo, Sept 30, 2011. [Photo/Agencies]

BEIJING - Three newly-crowned Grand Slam winners Li Na, Petra Kvitova and Samantha Stosur all suffered a downturn after winning the champion, while Kvitova expressed her determination to break the so-called Grand Slam champion curse here on Sunday.

Li of China failed to continue her form after the history-making triumph at Roland Garros, being knocked out of the first round of the China Open on Sunday, following her early exits at both Wimbledon and US Open.

Stosur of Australia lost the first round at the Pan Pacific Open after triumphing at the US Open, while Wimbledon champion Kvitova was also stunned in the first round of the US Open, and was stopped by Vera Zvonareva in the semi-finals last week in Tokyo.

Li admitted after taking the first Grand Slam champion, she felt more and more pressure on the court no matter whom she played with. Kvitova echoed by saying "it's very tough to be concentrate on the next matches(after winning the Grand Slam)."

"Everybody knows that we can win every tournament what we play. It's tough for us to be still on the court and play like before," said the 21-year-old Czech, "because you never be prepared for winning Grand Slam and what will be after the Grand Slam when you won."

Talking about her first-round exit at the US Open, Kvitova said it was because the difference on the hard court after the grass. "I mean, the tactics and techniques are different, so I need some time to be on the court and play my game again."

Last week at the Pan Pacific Open, despite the loss to Zvonareva, Kvitova's run to the semi-finals had already lifted her into the top five in the WTA rankings, and she was qualified for the year-end WTA championships for the first time.

"After US Open it was like again some days off, and then go back to Tokyo. There I felt OK and I played my game finally there, hopefully it will be continue here. It will be so nice play championships in Istanbul, you never know how it's going, so we will see."

Last year at the China Open, Kvitova lost to Caroline Wozniacki in the third round. "Hopefully I will play my best game this time, " added Kvitova.

The fifth-seeded enjoyed a first-round bye at this WTA premier event and will face the winner between Arvidsson Sofia of Sweden and Bondarenko Alona of Ukrain.