5 biggest upsets at the US Open 2015

Kei Nishikori US Open Paire
5th seed Kei Nishikori

#2 Petra Cetkovska def. Caroline Wozniacki

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Showing remarkable fearlessness at the biggest moments, 30-year-old Cetkovska of the Czech Republic, who was out for seven months with a hip injury, fought off four match points, spanking winners on every one of them, going on to score the biggest upset of this year's tournament, taking down Caroline Wozniacki, 6-4, 5-7, 7-6 (1) in a late night match in Arthur Ashe Stadium.

This was Wozniacki's third second-round loss at a major this season, along with the Australian Open and French Open. She made it to the fourth round at Wimbledon.

What is the foot injury that has troubled Rafael Nadal over the years? Check here