Fifth-seeded Slovenian Katarina Srebotnik beat German Sabine Lisicki 6-3, 6-1.
Eighth-seeded Chinese Zi Yan was trailing Mara Santangelo 5-6 in the first set when the Italian retired from their bout with a left foot injury, putting Zi in the round of 16.
Ukrainian qualifier Tatiana Perebiynis defeated American Ashley Harkleroad 6-2, 6-1 and Swiss Timea Bacsinszky beat former top 10 Australian Jelena Dokic 6-4, 6-2.
Selena Gomez drops F-bomb, walks off stage during Jingle Ball performance
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