'It's getting there with every match you start building up for the top battles starting now,' said Azarenka, who only needed 57 minutes to beat the 47th-ranked Vesnina. 'It's really exciting to be again so far in the tournament. 'Azarenka started last season with a 26-match winning streak, including a lopsided victory over Maria Sharapova in the Australian Open final.
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 successfully defend her Australian title to hold top spot from French Open champion Sharapova or Serena Williams, who won Wimbledon, the London Olympics and U.S. Open titles last year.
Next up for Azarenka is a quarterfinal against Svetlana Kuznetsova, who entered the season's first major ranked No. 75 but has previous 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 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 by beating another seeded player in the fourth round, defeating No. 21 Andreas Seppi 5-7, 6-3, 6-2, 6-2 on Monday.Chardy lost in the first round at Australia in the previous three years and his best run at Melbourne Park is the second round. Now is he guaranteed of a spot in the quarterfinals against either U.S. Open champion Andy Murray or No. 14 Gilles Simon.
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.
'I just had flashback of 2012,' said Djokovic, who ripped off his shirt to celebrate again, like he did last year.'It was maybe 45 minutes less this match than the one 12 months ago, but still it was still as exciting. I tried to enjoy the moment and couldn't ask for more.'
The win was Djokovic's 18th in a row at Melbourne Park after winning the last two Australian titles, and earned him a place in the quarterfinals of a 15th consecutive major.