Serena Williams (USA)  vs Flavia Pennetta (ITA) . For the second time in three years one quarter of the U.S. Open quarterfinalists are from Italy. The last time it happened the two Italians faced each other and for the last two years there has been an Italian semifinalist at the U.S. Open. However, I doubt that it will happen a third year in a row. Flavia Penetta has had her best results here in New York, and reached the semifinals last year (losing to Azarenka in two very ugly, error-prone sets). Unfortunately for Flavia, instead of being drawn to face Vika again, she has to play Serena, who, now that she is in the business end of a major for the first time in 2014 is more determined than ever to finally capture Major #18, especially since she is the only member of the WTA Top 10 left remaining in the draw. PREDICTION: Williams.
Ekaterina Makarova (RUS) 
Shuai Peng (CHN)
Agnieszka Radwanska (POL)  vs Jelena Jankovic (SRB)  Belinda Bencic (SUI). Peng is having a career-best performance in New York. She has already dismissed #4 seed Agnieska Radwanska, #14 Lucie Safarova and #28 Roberta Vinci to reach this far, so surely she won't falter against the unseeded teen sensation that is Belinda Bencic of Switzerland? Bencic, 17, is playing in her very first major quarterfinal, having surprised #9 Jelena Jankovic in a match only she and her coach Martina Hingis thought she could win. But Bencic won decisively. In some sense the Swiss player has had the more impressive road to get to this point, having dismissed two top 10 players (Jankovic and #6 Angelique Kerber). This match means so much to the players that it will almost certainly result in horrible tennis, and in the end it is very unlikely the victor will win their next match to reach their first career final. PREDICTION: Bencic.
Sara Errani (ITA)  vs. Caroline Wozniacki (DEN) 
Maria Sharapova (RUS) . Wozniacki played one of the best matches of her life to absorb and redirect Maria Sharapova's powerful groundstrokes to outlast the 5-time major champion and earn a stunning (and rare) victory over one of the Big Babes of women's tennis. After seeing her ex-fiance' Rory Mcilroy go on to win two major golf championships after ending their relationship, Wozniacki has been playing with increased intensity and verve all summer long, with good results to show for it (like taking Serna Williams to 3 sets in both Montreal and Cincinnati) . With the upset of multiple top seeds from her half of the draw, the Dane is now the highest rated player in her half of the draw and she has always been an expert in beating players she is supposed to beat while coming up short against players with more power and stature than she has. Surprisingly, these two players have only met three times on tour and although Wozniacki leads 2-1 she hasn't played La Grande Sara since the Italian became ensconced in the Top 10 of women's tennis. No matter, this is a golden opportunity for Wozniacki and I would be shocked if she didn't take advantage of it to reach her 2nd major final and a chance to (finally) win her first major title. PREDICTION: Wozniacki.