Stosur and qualifier Madison Brengle played for 2 1/2 hours before Stosur advanced with a 6-7 (4-7), 6-1, 7-6 (7-5) victory. Three breaks allowed Brengle the chance to take the first-set tiebreaker but Stosur dominated the second set -- losing eight points overall -- to even the match.
Both players served solidly in the third set before Stosur had the late spurt in the tiebreaker to get by the No. 147-ranked Brengle.
No. 2-seeded Kirsten Flipkens had a much easier time in a 6-4, 6-1 decision over Marina Erakovic. Flipkens saved three of the four break points she faced and finished off five breaks in 12 opportunities.
Alison Riske knocked off fourth-seeded Anastasia Pavlyuchenkova 6-3, 6-2 by saving all three break points she faced.
No. 7-seeded Klara Zakopalova defeated Yvonne Meusburger 7-5, 6-2 despite dropping serve five times. However, she had eight breaks in the 10 games Meusburger served. Also, eighth-seeded Bojana Jovanovski topped Annika Beck 7-5, 6-3.