Stosur didn't face a break point in rolling past Johanna Larsson 6-4, 6-2. Stosur lost only 12 points in nine games serving. She was particularly successful in the second set, dropping three points despite being good on less than half of her first serves.
While Larsson took a comfortable 62 percent of the points on serve, Stosur was able to finish off three of her nine break opportunities for the win.
No. 4-seeded Eugenia Bouchard dispatched Varvara Lepchenko 6-3, 6-0 with five breaks and seventh-seeded Monica Puig over three dropped service games in a 6-4, 6-4 win over defending champion Heather Watson.
A pair of Japanese players advanced as Misaki Doi routed Silvia Soler-Espinosa 6-1, 6-2 in 55 minutes and Kurumi Nara ousted Caroline Garcia 6-3, 6-2. Nara was helped by 12 doubles faults from Garcia, which contributed to six breaks.