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)

Victoria Azarenka is making her debut in our retrospections of players' yearly outfits, thanks to a kind request of our regular reader LuLinQa.

Azarenka is sporting Nike, and looking at all her 2009 outfits in one place I can say that they are the perfect choice for widespread use (in the large portion of Maria Sharapova’s you would stand out too much). All the outfits are well-designed, the colors are just right, and we know that Nike doesn't fail with the quality.

My favorite is the French Open dress, without doubt. I love the simple, yet interesting design, especially the back. The dress is the same as the one she wore in Miami, Rome and Madrid, but I prefer the blue Roland Garros version because it's more eye-catching.

Notice that headbands and visors are a must in Azarenka’s on-court appearance.

What do you think of Azarenka’s outfits? Which one is your favorite?

By the way, this is the first time we are doing a retrospection of players’ outfits in slides. Do you like this new medium?

Our dear reader Teerin is contributing to Women's Tennis Blog once again, this time by creating a countdown of the best moments in the 2009 tennis season.

Teerin would like to have been able to include more memorable situations, but YouTube videos can't be more than 10 minutes long. Which WTA moments would you add to Teerin's Top 10? I would include the emotional retirement of Ai Sugiyama and also, I would put Kim Clijsters' US Open win on top of the list.

Teerin, thank you so much for your continuous and active support of Women's Tennis Blog.

Dinara Safina handed a match to Jelena Jankovic, pulling out from the Sony Ericsson Championships in Doha when serving at 1-1 in the first set. The reason for the Russian’s withdrawal is a back injury, which is likely to prevent her from playing the start of the next season, including the 2010 Australian Open.

Safina said the bone structure in her lower back is "starting to fracture", and that she has had the injury for three months. Today, she couldn't handle the pain.

Jankovic lost her first round-robin match to Victoria Azarenka, so this present from Safina must have been welcome.

Safina regained the top-ranking on Monday, but she will again hand it to Serena Williams, who will finish a season at No.1 for the second time in her career.

Earlier in the day, Caroline Wozniacki beat Victoria Azarenka 1-6 6-4 7-5, recovering from a first set blowout and saving a match point in the third set. Azarenka was leading by a break four times in the decider, but Wozniacki fought back each time. It was Wozniacki's first match at the Sony Ericsson Championships ever. (photo via Sony Ericsson WTA Tour)

The first match of the Sony Ericsson Championships was between Victoria Azarenka and Jelena Jankovic. The Belorussian debutant at the Championships triumphed in straight sets 6-2 6-3, making 15 unforced errors compared to Jankovic’s 33.

The second match of the day featured defending champion Venus Williams and Elena Dementieva. Williams entered the encounter with an impressive 9-2 record against Dementieva, including six straight wins over the Russian. The American built a 6-2 3-1 lead in the match at the season-ending Championships, and looked to be extending her streak, when Dementieva fought back to eventually take a 3-6 7-6(6) 6-2 victory.

The first day of the round robin stage at the Sony Ericsson Championships was closed with Serena Williams’ tight win over Svetlana Kuznetsova, 7-6(6) 7-5. Williams came back from behind multiple times to have her revenge for the quarterfinal loss to Kuznetsova at the 2009 French Open. (photo: Ralf Reinecke)