Samantha Stosur will be relieved to have repelled the challenge of Nadia Petrova in relative comfort, running out a 6-3, 6-3 winner.
The Russian no.29 seed has proved a handful for Stosur in the past, and led 5-2 in their head-to-heads, including their most recent meeting in Indian Wells earlier this year which Petrova won 6-1, 6-7(6), 7-6(5).
Mindful of the challenge, the Australian sixth seed was a picture of concentration on Court No.1 and pounced on every chance that came her way in a scrappy match that was short on rallies.
Stosur was the more enterprising, hitting 20 winners to Petrova's 10, and crucially won four of the five break points that came her way. The Russian, twice a semi-finalist here, will feel frustrated at letting the match slip away, only converting one of four break points.
On such small margins are these matches won and lost, and Petrova's inability to make this a closer-run thing may explain why she has gradually slid down the rankings from a career high of No.3.
Stosur moves on to a fourth round match with American Sloane Stephens in which she will be a strong favourite.