Kvitová now joins seeded players Simona Halep of Romania, Poland's Agnieszka Radwańska, German Angelique Kerber and Ana Ivanovic of Serbia, who all made shock early exits in New York, while two-time champion Venus Williams has also been knocked out inside the first week.

Czech Kvitová had her right thigh heavily strapped during her match against the world number 145 Krunić, who had never won a Grand Slam match before arriving in New York.

However, she secured arguably the biggest win of her career as she despatched her more vaunted opponent 6-4, 6-4 to set up a clash with last year's runner-up Belarusian Victoria Azarenka in the next round.

"I'm very disappointed," said Kvitová, whose exit leaves only five of the top-10 women's seeds left in the tournament.

"I wanted to win today, and unfortunately I didn't.

"She played really unbelievable tennis and she put a lot of balls back.

"For me it was very difficult just to play only on the winners."

Elsewhere in the women's draw, Serena Williams made it a hat-trick of victories over fellow Americans as she overcame Varvara Lepchenko 6-3, 6-3.

World number one Williams has yet to drop a set as she chases a third consecutive title at Flushing Meadows and will play Estonian Kaia Kanepi, who upset 15th seed Carla Suárez Navarro of Spain 7-5, 6-0.

Canadian seventh seed Eugenie Bouchard defeated Czech Republic's Barbora Záhlavová-Strýcová 6-2, 6-7, 6-4, while Italy's 11th seed Flavia Pennetta comfortably saw off American Nicole Gibbs 6-4, 6-0.

Petra Kvitová looks down and is out of the US Open after defeat to Aleksandra Krunić ©Getty Images



Meanwhile, Briton Murray and Serbia's Djokovic came through their matches with relative ease.

Murray was taken to four sets by Russia's Andrey Kuznetsov as a number of double faults and unforced errors made it harder than it possibly should have been.

The 2012 champion eventually came through 6-1, 7-5, 4-6, 6-2 despite dropping his serve four times against the world number 96.

"The first couple of sets were pretty good and then I started a bit slow in the beginning of the third," said Murray, who has yet to win a title this year.

"He gained confidence from that and he definitely started hitting the ball better in the third set.

"I'm happy I stayed solid.

"It was tough."

He will now take on Jo-Wilfried Tsonga of France after he eased passed Pablo Carreño of Spain in straight sets, 6-4, 6-4, 6-4.

Tsonga beat Murray in Toronto earlier this month but the Scot has a 9-2 career record against the Frenchman.

Andy Murray secured a place in the fourth round at the US Open despite a patchy performance against Andrey Kuznetsov ©Getty Images



Top seed Djokovic had no trouble against Sam Querrey of the US and will take on Germany's Philipp Kohlschreiber next after the 6-3, 6-2, 6-2 win.

Kohlschreiber knocked out American John Isner 7-6, 4-6, 7-6 ,7-6 to make it the third year in-a-row he has ended Isner's stay in the US Open.

Australian Open champion Stan Wawrinka of Switzerland was awarded a walkover after his opponent Blaž Kavčič of Slovenia withdrew due to a foot injury.

Spain's Tommy Robredo beat Australian Nick Kyrgios 3-6, 6-3, 7-6, 6-3, while Canada's Milos Raonic beat Víctor Estrella Burgos of Dominican Republic 7-6, 7-6, 7-6.

At 34, Estrella Burgos became the oldest ever debutant at the US Open this year.

Contact the writer of this story at [email protected]


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