She moved to No. 1 in the rankings with that win and has remained there for all but a few weeks.
But she needs to defend her Australian title to hold the top spot from French Open champion Sharapova or Serena Williams, who won Wimbledon, the London Olympics and U.S. Open titles.
Next up for Azarenka is a quarterfinal against Svetlana Kuznetsova, who entered the season's first major ranked No. 75 but has won titles at the 2004 U.S. Open and 2009 French Open.
Kuznetsova was given a time warning for taking too long during a changeover in her 6-2, 2-6, 7-5 win earlier Monday over former No. 1-ranked Caroline Wozniacki, but said it didn't bother her.
As for Wozniacki, after twice failing to win her breakthrough major as the No. 1-ranked woman at the Australian Open, she is now expected to drop out of the top 10 after a fourth-round loss that follows back-to-back first-round exits at Wimbledon and the U.S. Open.
Kuznetsova is moving in the other direction on her comeback from a right knee injury that ruled her out of the last U.S. Open, ending a run of contesting 40 consecutive majors. And she's looking forward to taking on Azarenka.
"The time I played in Indian Wells was totally a disaster. I got [beaten] very badly," she said. "But, I mean, she's tough; she's No. 1; I have nothing to lose; she has all the pressure.
"I know I got the game to give her some problems, and I will just do my best and just try to enjoy it."
Serena Williams was playing her fourth-round match against No. 14 Maria Kirilenko later Monday.
On the men's side, Frenchman Jeremy Chardy followed up his upset win over 2009 U.S. Open champion Juan Martin del Potro by ousting another seeded player in the fourth round, beating No. 21 Andreas Seppi 5-7, 6-3, 6-2, 6-2 on Monday.
Play on Day 7 ran into Day 8 overnight, when Novak Djokovic needed just over 5 hours to beat Stanislas Wawrinka 1-6, 7-5, 6-4, 6-7 (5), 12-10 in a fourth-round match Sunday night, on the same court where he needed 5:53 to beat Rafael Nadal in last year's final.
P Monday, 7 p.m.
TV • ESPN2
Storylines On to the quarterfinals
R Defending women's champ Victoria Azarenka beats Elena Vesnina 6-1, 6-1.
• Svetlana Kuznetsova beats Caroline Wozniacki 6-2, 2-6, 7-5.