Danish fourth seed Caroline Wozniacki was ousted from the US Open on Thursday by 149th-ranked Czech Petra Cetkovska, leaving only three of the top-10 women in the event.

Cetkovska outlasted Wozniacki 6-4,5-7 7-6 (7-1) in a night match at Arthur Ashe Stadium to book a third-round match against Italian 26th seed Flavia Pennetta.

With the departure of former world No.1 Wozniacki, the US Open runner-up in 2009 and 2014, the only top-10 seeds remaining in the year’s final Grand Slam tournament from the original draw are top-ranked Serena Williams, Romanian second seed Simona Halep and Czech fifth seed Petra Kvitova.

Wozniacki wasn’t the only major casualty on the day with Wimbledon finalist Garbine Muguruza sent packing by red-hot Briton Johanna Konta 7-6 (7-4) 6-7 (7-4) 6-2.