Karolina Pliskova (CZE)  vs. CoCo Vandeweghe (USA) . Pliskova needs to reach the finals again to preserve her #1 ranking, while the American is finally beginning to fulfil her potential from winning the girls title here in 2008. This year CoCo has reached three major quarterfinals, and she has 1-1 record. These two have played four times on tour so far and split the results; Pliskova won their last meeting in Stuttgart this year and they also split their 2 hard court matches. Clearly the Czech player does not have problems with facing a hostile American crowd since last year she dispatched Venus Williams and then Serena Williams to reach her first major final. CoCo has clearly improved recently (perhaps due to the influence of coach Mats Wilander), she is less volatile on the court, which is aligning her results with her confidence (and self regard). However I still give a slight edge to the more experienced player, although I would not be surprised to see either player win. PREDICTION: Pliskova.
Madison Keys (USA) 
Venus Williams (USA)  vs. Petra Kvitova (CZE) 
Garbine Muguruza (ESP) . This quarterfinal is worthy of a major final. The two players have a combined 9 major titles between them. Kvitova got here by putting one of her dazzling displays of power and accuracy against the pre-tournament favorite (and reigning Wimbledon champion) Garbine Muguruza in the round before. That 7-6(3) 6-3 match is the highlight of the women's tournament to date, but this showdown is expected to rival that. Venus is here because she is playing some of the best tennis in her career in 2017, having reached (and lost) two major finals (Australia and Wimbledon) this year, 9 years after her last one, and 6 years after the diagnosis of an auto-immune disorder. Unfortunately, history does not bode well for Venus in this matchup, since she has only won one of their 5 meetings. However, every single one has gone to 3 sets and I fully expect that to happen here. In fact, I am basing my prediction on the belief that Kvitova will not be able to maintain the high level of play she has so far demonstrated in her first four matches (coming through without losing a set). If that does happen, then even Venus will not be able to stop Kvitova from winning her 3rd major. PREDICTION: Venus.
Anastasja Sevastova (LAT) 
Simona Halep (ROU)  vs. Sloane Stephens (USA). For the second year in a row Sevastova delivered a major upset at the U.S. Open. Last year it was taking out Muguruza and this year it was taking out Maria Sharapova. She has only ever reached two major quarterfinals and they both have happened in New York. She will face a resurgent Sloane Stephens who is finally capitalizing on her athletic abilities to simply refuse to lose matches. This is an incredible opportunity for American tennis to demonstrate what the post-Williams future of tennis will look like. Interestingly, all three non-Williams American quarterfinalists have reached major semifinals on hard courts, but in Australia (Stephens in 2013, Keys in 2015 and Vandeweghe in 2017) not New York. I'm fairly confident that streak will end this year. There's also a reasonable chance of an all-American final for the first time since Serena beat Venus in 2002. PREDICTION: Stephens.