Serena Williams believes she must improve if she is to lift her fifth Venus Rosewater Dish.
After straight-sets wins over Barbora Zahlavova-Strycova and Melinda Czink, the American was below par against China's Jie Zheng on Saturday, before triumphing 6-7, 6-2, 9-7.
The 30-year-old needed to dig deep to see off the 25th seed to move into the last 16, where she today faces Sara Errani's tormentor-in-chief Yaroslava Shvedova, who pulled off a golden set – winning 6-0 without dropping a point – against 10th seed Errani.
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