Maria Sharapova, who was to be the No.3 seed, withdrew before the tournament due to a leg injury. But what happened to the other six Top 10 seeds? Here are the underdogs who've been rising up:
Petra Cetkovska (CZE)
The big-hitting Czech overpowered No.4 seed Caroline Wozniacki in the second round on Thursday night, 6-4, 5-7, 7-6(1), saving four match points along the way. It was her 10th career Top 10 win.
Lesia Tsurenko (UKR)
Another big-hitter, Tsurenko outslugged No.6 seed Lucie Safarova in the first round on Tuesday morning, 6-4, 6-1, and in the process improved to 5-2 - yes, 5-2 - against Top 10 players this season.
Dominika Cibulkova (SVK)
A former World No.10 and Australian Open finalist, Cibulkova needs no introduction, really - and in the very first match of the fortnight on Ashe, she dispatched No.7 seed Ana Ivanovic, 6-3, 3-6, 6-3.
Anna Tatishvili (USA)
This Georgian-born American had never even beaten a Top 20 player in her career, let alone a Top 10 player. But she dropped a 6-2, 6-1 defeat onto No.8 seed and WTA Rising Star Karolina Pliskova.
Johanna Konta (GBR)
Konta didn't just upset No.9-seeded WTA Rising Star Garbiñe Muguruza on Thursday, 7-6(4), 6-7(4), 6-2, but at three hours and 23 minutes it was the longest recorded women's match in US Open history.
Denisa Allertova (CZE)
The WTA's third-fastest server of the year, Allertova served up a big upset on Day 1, taking out No.10 seed Carla Suárez Navarro, 6-1, 7-6(5). It was also the young Czech's first Top 10 win.