Sobs turned to lobs as Dinara Safina stormed into the quarterfinals of the US Open, defeating German Anna-Lena Groenefeld 7-5, 6-0 on Monday.

Safina, who sometimes lets her emotions get the best of her, had to be talked into taking to the court against qualifier and 141st-ranked Groenefeld on the 10,000-seat Armstrong Stadium by her coach Zeljko Krajan.

"After the warm up I just started to cry. I could not stop crying," Safina said. "My coach said, 'Just go out there'. I said, 'I cannot push anymore myself'. He said, 'We know that you're not a machine. Just go out there and don't think," she informed.

"He told me again, 'just please don't show me any emotions, like these negative emotions. If you want, don't show even positive. Just go on the court and do whatever you can on this day. Slowly I started to feel like I still can push myself. I am really happy that I won," said the Russian.

It's already been an incredible year for Safina and a win at the US Open would be a fitting exclamation point for the 22-year-old Russian.

But winning three titles and reaching the final of six of seven tournaments since the start of May is also wearing on her nerves and body.

"He (Krajan) said if it's 20 percent left from your body, just give this 20 percent. Don't use another percent just throwing the balls around and shouting," Safina said.

Safina is trying to follow in the footsteps of brother Marat and win her first Grand Slam at the US Open.

Safina moves through to the quarterfinals where she will square off against Italy's Flavia Pennetta who dominated former world number one Amelie Mauresmo of France 6-3, 6-0.

"I'm very happy about this tournament. In the beginning, I never think to get in the quarter-final and to have this chance. I didn't start with a good tournament, because my first match was very tough. I didn't play my best tennis. But I just try to fight every point and keep going," Pennetta said.

Safina was runner-up at the French Open earlier this year, giving credence to the argument she is the most in form of all the women's players on the WTA Tour.

Marat won his initial Grand Slam at the US Open in 2000 and Safina, who won the silver medal at the Beijing Olympics, is hoping to do the same.

"It will be the dream come true," she said. The special bond she has with her brother and Krajan has helped her reach her full potential.

"I have grown up a lot in the mind. A year ago I would not be able to do these kind of things. Even the match before against (Timea) Baczinsky (third round) I would have already lost. But somehow I started like to control better myself," she said.

"If you have a trust in your coach and you know he understands you and I understand him so that makes it easier for me to express my emotions. Some coaches don't want to hear that you are tired. Or maybe they will not believe you that you are tired. They will say, 'No, this is an excuse because you don't want to lose'. Of course, if I go on court then I want to win," added Safina.

Elena Dementieva and sixth seed Safina are the only Russian women remaining in the singles draw - the lowest Russian representation at a Grand Slam since 2004.

And like Dementieva, Safina can stake her claim to the world number one ranking with a successful finish in this final major championship of the season.

If Safina wins the singles title she would become the number one if second seed Jelena Jankovic does not advance past the semifinals. And she is not the only one in action Monday with a shot at the top ranking.

Serena Williams, who takes on wild card Severine Bremond of France in the night session, also has a chance to supplant Serbian star Ana Ivanovic, who suffered a shock early round exit last week.

"It's open," she said. "It's not only me. Right now Dementieva is playing really good tennis. The Williams sisters and Jankovic. Whoever is left in the draw has a chance. Let's see who really deserves that spot."

Pennetta, who competed for Italy in the Beijing Games, says she will have to step up her play against Safina.

"She's in good shape," Pennetta said of the Russian. "I have to serve. My first serve is going to be important, also the return."