In the third-round match yesterday, Petrova advanced when Galina Voskoboeva was forced to retire with a back injury after losing the first set 6-1.
She will face seventh-seeded fellow Russian Vera Zvonareva, who beat Italian Sara Errani 6-4, 6-1. Petrova holds a 5-1 record against her countrywoman.
Petrova's shortened match could be a boon for her, who has been struggling to recover from the meningitis that forced her to withdraw from a tournament in Auckland early this month.
"It is very nice and it is very unexpected because I got ready for a battle out there," Petrova said.
"I really wanted (to win) this match not only because I made the fourth round last year but for proving to myself that after such a hard time that I can still come back and perform at the top level."
"I'm good, quite happy actually. I had a difficult week in Sydney (she lost in the first round). I wasn't strong enough and I really didn't trust my body up there, so I just wanted to test the waters.
"But I'm very happy with my general feeling right now. I feel like every day I'm getting stronger and it's really helping me in my matches."
(Via theage.com.au; Images by Scott Barbour/Clive Brunskill/Getty Images AsiaPac via zimbio.com)