Li Na has reached a career-high ranking of No. 2 this week. (Paul Crock/AFP/Getty Images)

Australian Open champion Li Na of China moved up to No. 2 in this week's WTA Tour rankings, the highest position for a singles player from Asia, male or female, in history.

Li, who lost in the third round of the Qatar Open last week, rose from third to second as part of a shakeup behind No. 1 Serena Williams. The new top five is Williams, Li, Agnieszka Radwanska, Victoria Azarenka and Maria Sharapova. Radwanska improved one spot, claiming her highest position in more than 16 months, and Azarenka was bumped from No. 2 to No. 4 after withdrawing from the Qatar Open as the two-time defending champion. Sharapova remains fifth.

Li's milestone comes the same week that countrywoman Peng Shuai ascended to No. 1 in doubles, becoming the first top-ranked Chinese player.

In other rankings news:

• Romania's Simona Halep inched up one spot, to a career-high No. 9, after winning the Qatar Open. The highest-ranked Romanian ever is Irina Spirlea, who reached No. 7 in 1997.

• Sara Errani fell from No. 7 to No. 10.

• Former No. 23 Mona Barthel slipped from No. 63 to No. 76. Barthel, who opened the year at No. 34, has lost in the first round in three of five tournaments this year.