(CNN) -- Day six of the U.S. Open at Flushing Meadows and the shocks just keep on coming in the women's draw.
Reigning Wimbledon champion Petra Kvitova is the latest casualty after crashing out in the third round to Aleksandra Krunic, a player ranked 145 in the world.
The Serbian qualifier made light work of the heavy-hitting opponent from the Czech Republic winning in straight sets 6-4 6-4 in one hour 34 minutes.
To say that Kvitova was off her game is an understatement as she lost serve five times and racked up 34 unforced errors. But rather than focus on the shortcomings in her own game on Saturday, Kvitova chose to praise her opponent.
"I think she played really unbelievable tennis, and she put a lot of balls back," Kvitova said.
"I did mistakes, and I was really trying everything that I could in that moment. I was trying to fight and fighting every point, but it was so difficult. It wasn't really my day. She played really great tennis today."
By her standards, Kvitova has a poor record at the U.S. Open having never got further than the fourth round.
But the 24-year-old had reason to hope that this year might be different after claiming a second Wimbledon title in July and her win at the New Haven tournament last week.
But her dreams have been extinguished for another 12 months as she becomes the fifth top 10 seed to depart the women's tournament.
Kvitova joins second seed Simona Halep, fourth seed Agnieszka Radwanska, sixth seed Angelique Kerber and Ana Ivanovic, the eight seed -- all of whom have already packed their bags.
For Krunic, who will now play Belarusian Victoria Azarenka in the fourth round, it was a victory to savor.
"It was an honor for me to be in the same court with Petra. Of course, I didn't expect to win. Of course, I was hoping at least to win a set, but I managed to win a match somehow."
Azarenka, seeded 16 at Flushing Meadows this year, eased through to the last 16 with a 6-1 6-1 win over Russia's Elena Vesnina.
Reigning champion Serena Williams is also safely through to the second week following a 6-3 6-3 win over Varvara Lepchenko while 11th-seed Flavia Pennetta from Italy will face Australia's Casey Dellacqua for a place in the quarterfinals.
Pennetta saw off Nicole Gibbs of the U.S. in straight sets 6-4 6-0, while Dellacqua, the 29th seed, needed three sets to get past Karolina Pliskova, winning 6-3 3-6 6-4 in one hour 54 minutes.
In the men's competition, the top seeds are faring better.
Champion of two years ago Andy Murray, seeded eighth this year, progressed to the fourth round with a four-set win over Russia's Andrey Kuznetsov 6-1 7-5 4-6 6-2.
"I got off to a good start, then had a bit of a cushion when he started to get back in the match," Murray said. "I just tried to stay solid in the fourth set and thankfully it paid off."
The 27-year-old Scot's reward is a match up against Jo-Wilfried Tsonga.
The French ninth seed beat Spain's Pablo Carreno Busta in straight sets 6-4 6-4 6-4.
World No. 1 Novak Djokovic didn't break sweat against Sam Querrey, beating his American opponent 6-3 6-2 6-2 to set up last 16 tie against either Philipp Kohlschreiber or American 13th seed John Isner.
Earlier on Saturday, Milos Raonic won in straight sets against Victor Estrella Burgos of the Dominican Republic.
The number five seed from Canada will now play 10th seed Kei Nishikori in the last 16. The Japanese No. 1 beat Argentina's Leonardo Mayer 6-4 6-2 6-3.