Azarenka withdrew from her scheduled semifinal versus Williams because of a toe injury on her right foot. Azarenka said the toe was infected and she had "minor surgery" on it Thursday.
She said she decided on immediate medical action because the Australian Open starts in 10 days.
The injury was similar to one suffered by Williams recently and led to her pulling out of a scheduled exhibition against Azarenka last month in Thailand.
Williams, the No. 3 seed at Brisbane, will face Anastasia Pavlyuchenkova in the tournament finals. Pavlyuchenkova got past Lesia Tsurenko -- who replaced the injured Maris Sharapova in the draw -- 4-6, 6-1, 6-2 in a 2-hour match Friday.
Pavlyuchenkova dropped serve three times in the first set but only once after that in advancing to her fifth WTA title match. She's 3-1 in prevision title appearances.
Williams, 51-2 in matches since last March, is 3-0 lifetime versus Pavlyuchenkova. She is 46-15 in WTA championship matches. The 46 titles are the most among active WTA players.