INDIAN WELLS, CA, USA - The fourth round wrapped up at the BNP Paribas Open on Tuesday night, with Caroline Wozniacki the last player into the last eight - and a match with Victoria Azarenka looming.

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The No.8-seeded Wozniacki had to use all of her guile and lift her game on just about every big point there was but she managed it, rallying from 5-3 down to win a marathon 65-minute first set then taking a simpler second set to move past a No.10-seeded Nadia Petrova in a tight two-setter, 76(3) 63.

It was redemption in a way - though Wozniacki had won four of their six previous meetings, their last one was a somewhat forgettable memory, as Petrova handed her a 62 61 loss in Sofia last November.

"Last time I lost to her I think it was 1 and 2 or 2 and 1, but the score doesn't really justify the match, because I thought it was a really close match," Wozniacki commented. "Today I was returning way better and I got a lot of returns in. We had a lot of rallies, but I felt like I was on top of most of them.

Next up for Wozniacki is the No.1 seed and defending champion, Victoria Azarenka, who defeated Urszula Radwanska earlier on in the day, 63 61. Azarenka is now an incredible 17-0 on the year so far.

"It was pretty obvious I wasn't feeling that well - my ankle was bothering me, it's been bothering me for a while, and it hasn't really been getting better," Azarenka said after the match. "But on the bright side, I won the match today. I overcame those things and - I don't know how - managed to just take my opportunities and really go for my shots and make it happen, and not just wait for her mistakes.

"She's a very, very consistent player and doesn't miss, so I had to take everything in my own hands."

And on the 17-match winning streak? "I never think about winning streaks," she said. "I have big self-belief. I just know the things I have to do. Sometimes it will not work out. But if I have good intentions, a good mindset and know exactly what to do on the court, the outcome is not that important for me."

Wozniacki leads Azarenka in their head-to-head, 4-2, though there's a very big asterisk - they haven't played in two years, since this same round at this tournament in 2011, long before Azarenka won her first Grand Slam title and got to No.1 - in fact even before the Belarusian cracked the Top 5.

"Victoria has improved in a few ways that have helped her a lot," Wozniacki said. "I think I'm playing well. She's obviously playing well. I'm looking forward to playing her again. We'll see what happens.

"I definitely need to bring my A-game."

"Not that our games have changed tremendously, but in these two years a lot of things happened - a lot," Azarenka said. "But I think she's a terrific player. She knows how to play big matches and she knows to bring the A-game when it's needed. It will definitely be an interesting challenge."

Azarenka was asked how much better she is now than here two years ago. "Maybe 50%," she said.

The other quarterfinal on the top half of the draw will feature No.4 seed Angelique Kerber against No.7 seed Samantha Stosur, after Stosur rallied from a set down to beat No.24 seed Mona Barthel, 46 62 63, and Kerber edged Spanish qualifier Garbiñe Muguruza in a tight two-setter at night, 64 75.

Stosur has beaten Kerber in both previous meetings, most famously in the 2011 US Open semifinals.