Former world number one Justine Henin, playing only her second tournament since coming back to the WTA Tour and her first Grand Slam since the 2008 Australian Open, beat 19th seed Nadia Petrova to reach the semifinals at the Melbourne Park. The Belgian’s opponent in the last four will be second-time Grand Slam semifinalist China’s Zheng Jie, one of the most responsible players for putting China on a tennis map.

The seven-time Grand Slam champion Henin, a wildcard in Melbourne, had to dig deep to beat Nadia Petrova 7-6(3) 7-5. Both players struggled to hold serve, but it was Petrova who made 41 unforced error to Henin’s 26. Nevertheless, Petrova’s 2010 Australian Open run will be remembered, as she took out third seed Svetlana Kuznetsova and 15th seed Kim Clijsters out of the tournament.

Unseeded Zheng Jie advanced by stopping Russia’s Maria Kirilenko 6-1 6-3 in the quarterfinals. Kirilenko had an astounding tournament, but in the match against Zheng she was always a step behind, and the fact that her thigh was heavily strapped didn’t help either. We should note that Kirilenko played singles, doubles and mixed doubles during the tournament, and she’s still alive in the doubles competition, partnered with Agnieszka Radwanska.

The remaining semifinalists will be known after the Serena Williams vs. Victoria Azarenka and Venus Williams vs. Li Na matches are finished. (photos via Australian Open)

The fourth round came to a close on Day 8 of the 2010 Australian Open. Both Serena and Venus Williams progressed, as well as Chinese Li Na and Belorussian Victoria Azarenka.

Top seed Serena Williams routinely defeated home favorite Samantha Stosur 6-4 6-2 in the fourth round. The impressive performance by the American saw her lose only seven points on serve throughout the match, including one double-fault in the second set.

Serena’s opponent in the quarterfinals will be seventh-seeded Victoria Azarenka who won the day’s final match, coming back from a set down to beat Russian Vera Zvonareva 4-6 6-4 6-0 in almost two and a half hours.

Venus Williams had more trouble advancing to the quarterfinals than her sister Serena. The sixth seed lost the first set and was a break down in the second before recovering for a 3-6 6-2 6-1 victory against Italian Francesca Schiavone.

Next for Venus will be seed No.16 Li Na of China who upset fourth seed Caroline Wozniacki 6-4 6-3 to join countrywoman Zheng Jie in the last eight, thus making history for China – it is the first time two Chinese players are in the quarterfinals of a Grand Slam event. Li Na and Venus Williams have had only one career meeting, at the 2008 Beijing Olympics, and the winner was Li.

Other quarterfinal pairs include Justine Henin vs. Nadia Petrova and Zheng Jie vs. Maria Kirilenko. (photo via Australian Open)

World No.58 Maria Kirilenko, who took out Maria Sharapova in the first round of the Australian Open, reached her first Grand Slam quarterfinal through Dinara Safina’s misfortune of a recurrent back injury.

The second-seeded Safina retired down 5-4 in the opening set of the fourth-round match, with the same low back injury that forced her out of the Sony Ericsson Championships in Doha at the end of last season.

Safina’s injury is extremely painful: "I just cannot move anywhere. I mean, the physio asked me to lie on the table. I said, I cannot lie. I cannot make any movement. Whatever I try to move, it hurts terribly." And to make things worse, Safina thinks she may have even worsened the injury because she continued to play the match.

Kirilenko, on the other hand, has problems of her own. She turns 23 on Monday, but will have to postpone her birthday celebrations: "I don't want to get drunk before my next match. It's going to be difficult for me to play then."

Unseeded Kirilenko will play China's Zheng Jie, also unseeded, in the quarterfinals. Zheng holds a 4-1 head-to-head lead over the Russian. (photo via Australian Open)

Seed No.19 Nadia Petrova crushed former world No.1 Kim Clijsters in the third round and her new attitude towards tennis is still proving to be fruitful as she has now knocked out third seed Svetlana Kuznetsova.

On the same court where she scored a ruthless 6-0 6-1 victory over Clijsters, Petrova defeated French Open champion Kuznetsova 6-3 3-6 6-1 to reach the Australian Open quarterfinals.

"When I played Kim, before going on court, I said, 'it's all or nothing, I gotta to give everything' (and) I did," said world No.19 Petrova.

"Same thing happened today. If I can continue doing this, I can get even further."

Petrova’s next opponent will be seven-time Grand Slam champion Justine Henin, who advanced to the last eight despite sustaining an ankle injury in the third set of her fourth-round match against fellow Belgian Yanina Wickmayer. Henin defeated Petrova in 12 of their 14 encounters, including their meeting at the Brisbane International this season. However, Petrova is very likely to test Henin’s physical readiness. (photo via Australian Open)

World No.35 Zheng Jie was the first player to reach the 2010 Australian Open quarterfinals after a 7-6(5) 6-4 upset of seed No.31 Alona Bondarenko.

Zheng has now become the first Chinese ever to reach the quarterfinals of the Australian Open, while two years ago at Wimbledon she became the first player from her country to reach semifinals of a Grand Slam event.

"I feel tennis is going up very quickly in China," said Zheng who played a large role in raising the popularity of the sport in her country. "We have a good tournament, the China Open, and you can see lots of the newspapers talking about tennis much more now. We have more top players now too."

Zheng will face Russian Maria Kirilenko in the quarterfinals. (photo via Australian Open)