New York: In one of the biggest upsets at the 2016 US Open so far, Anastasija Sevastova held her nerve to dispatch No.3 seed and reigning French Open champion Garbiñe Muguruza, 7-5, 6-4 in the second round at Flushing Meadows on Wednesday.

Sevastova took the first set and raced out to a 5-1 lead in the second, holding two match points in the next game.

"I stopped thinking. I was thinking too much at 5-2, 5-3. Then I said, 'Okay, I have one more chance at 5-4. She's serving. I broke her before enough times, so I will try this one more time. And still, even then it's only 5-5. It's still an open match like the first set," said the Latvian, who broke Muguruza’s serve to love to clinch the match.

"I think it was a very tough match," Muguruza said after the match. "I think I didn't play well today. I think she also played well. Everything she was doing was working.”

Sevastova will now play against is Kateryna Bondarenko, who won a dramatic 5-7, 7-6(5), 7-5 match over China's Zheng Saisai.

Meanwhile, two-time finalist Caroline Wozniacki fought back from a 0-4 deficit in the opening set to upset No.9 seed Svetlana Kuznetsova, 6-4, 6-4 for a spot in the third round of the US Open. Wozniacki will now play Monica Niculescu in the third round after the Romanian advanced with a 6-0, 6-1 win over countrywoman Ana Bodgan.

No.8 Madison Keys and No.14 seed Petra Kvitova, too, notched straight set wins on their way to the third round at the US Open. Keys defeated fellow American Kayla Day in straight sets 6-1, 6-1 in just 49 minutes. However, Kvitova faced a stern challenge from Turkish trailblazer Cagla Buyukakcay, 7-6(2), 6-3. Kvitova will face the No.22 seed Elina Svitolina for a spot in the fourth round.

Meanwhile, CiCi Bellis defeated fellow American Shelby Rogers. Bellis stormed back from a set down to win convincingly, 2-6, 6-2, 6-2.