This will be a test if the real Ana is back. The Serbian was impressive in her matches so far, defeating in form players like Davis and Pennetta. She will be put to the test by wild swinging Kvitova. The Czech has had a miserable season, and I think Ana has a good chance here. She just needs to steady and wait for Kvitova's errors.
Pick: Ivanovic in 3 sets
Just when I thought Venus was playing well, she struggles mightily against Casey Dellacqua. Cibulkova will definitely be a tougher test for Venus, having beaten the American before. Still, I believe Venus has a chance. She needs to destroy Dominika's serves and try to keep her first serve percentage up. The Slovak will not be going down without a fight though.
Pick: Williams in 3 tight sets
Shaky Serena has been struggling to find her rhythm for her past two matches. Thankfully, she has a relatively easy opponent now. Coco blows hot and cold, so Serena just needs to weather the storm and make Vandeweghe move around the court. I expect a much cleaner match from the world number one this time.
Pick: Williams in 2 sets
Sure win bets: Maria Sharapova, Agnieszka Radwanska, Caroline Wozniacki
Upset alert: Angelique Kerber, Dominika Cibulkova, Petra Kvitova