The bottom half of the draw will play their fourth round matches Sunday, with Agnieszka Radwanska versus Ana Ivanovic one to watch.
WTA Staff

MELBOURNE, Australia - Fourth round play will get underway Sunday, with Agnieszka Radwanska's continuing quest for her first major and Maria Sharapova being practically perfect among the storylines.

Sunday, Fourth Round
Rod Laver Arena
[4] Agnieszka Radwanska (POL #4) vs. [13] Ana Ivanovic (SRB #13)
Radwanska leads 4-3
Victorious in Auckland and Sydney to kick off her 2013 season, Agnieszka Radwanska is one of just six players to capture two pre-Australian Open events since the tournament took its current place on the calendar in 1987. Her Sydney triumph was especially noteworthy, in that her 60 60 rout of Dominika Cibulkova in the final was the first such scoreline in a WTA final since November 2006. And while the superb performances of Maria Sharapova and Serena Williams have garnered more attention during the first week in Melbourne, Radwanska has quietly continued her pre-Australian Open dominance. In dropping just 15 games, she has improved her 2013 record to 12-0, each of them straight-setters.

This will be Radwanska and Ivanovic's biggest showdown to date, as they have never met this deep into a major. After dropping their first three match-ups, Radwanska has won four in a row. However, Ivanovic should not be overlooked, as she recorded an impressive straight set defeat of fellow Serb and former World No.1 Jelena Jankovic in the third round. Also, she has now made at least the fourth round in five of her last six majors.

[2] Maria Sharapova (RUS #2) vs. Kirsten Flipkens (BEL #43)
Sharapova leads 2-0
In winning her first two matches here, 60 60, Maria Sharapova became the first player since Wendy Turnbull at the 1985 Australian Open to record consecutive 60 60 victories at a major. And then in the third round against much tougher opponent Venus Williams, Sharapova dropped just four games - making this the most efficient run to the fourth round of the Australian Open since Steffi Graf also surrendered four games in her first three matches en route to the 1989 title.

As for fourth round opponent Kirsten Flipkens, the Belgian picked up her first WTA title in Québec City during a breakthrough 2012, and she has continued that form in 2013. A quarterfinal appearance in Auckland followed by a semifinal showing in Hobart led to her making her Top 50 debut, and three more wins so far this week have improved her 2013 record to 8-2 and put her into her first Grand Slam fourth round. All that being said, it would be a monumental upset were she to down Sharapova, against whom she has failed to win a set in two matches.

[5] Angelique Kerber (GER #5) vs. [19] Ekaterina Makarova (RUS #19)
Kerber leads 3-2
In an all-lefty affair, Angelique Kerber and Ekaterina Makarova will face off for the right to play the Maria Sharapova-Kirsten Flipkens winner. Kerber has yet to drop a set this week in getting to the fourth round here for the first time, while Makarova lost one, but it was during an impressive defeat of World No.11 Bartoli in the third round. In her series with Makarova, Kerber was beaten in the first two matches, but then won three straight - each of those victories coming last year.

Makarova's rise to prominence came here last year, as she shocked Serena Williams in the fourth round en route to her first and only run to a Grand Slam quarterfinal. She will be trying to turn around a trend that has seen her go just 1-14 against Top 5 opponents, though the lone win did occur against another lefty - then-No.4 Petra Kvitova at Eastbourne last year.

Around the grounds?
Over on Hisense, 2011 Australian Open runner-up Li Na squares off with Julia Goerges. And on Margaret Court, the Williams sisters and Sara Errani and Roberta Vinci both have third round doubles encounters in which wins would pit them against each other in a compelling quarterfinal.