Aleksandra Krunic during the match against Petra Kvitova, at Flushing Meadows, on Saturday. (AFP)

New York: Third seed Petra Kvitova was ousted by 145th-ranked qualifier Aleksandra Krunic of Serbia 6-4, 6-4 in the third round of the US Open on Saturday, joining a long list of upsets in women’s singles.

The 21-year-old Krunic, who aims to graduate from university in Serbia this year with a degree in economics, shocked the error-prone Czech with relative ease.

Wimbledon champion and top seed Novak Djokovic led an unfettered charge of seeded men into the fourth round, beating American Sam Querrey 6-3, 6-2, 6-2.

Andy Murray double-faulted to send the match to a fourth set, but then swiftly took care of business in a 6-1, 7-5, 4-6, 6-2 win over Russian Andrey Kuznetsov to reach the fourth round.

Also advancing early in Saturday’s day session were fifth-seeded Milos Raonic and 10th seed Kei Nishikori of Japan. Raonic won 7-6, 7-6, 7-6 against Dominican Victor Estrella Burgos, while Nishikori booked his berth in the round of 16 by beating 23rd seed Leonardo Mayer of Argentina 6-4, 6-2, 6-3.

Kvitova, who made 34 unforced errors in the 98-minute match against the quick-moving Serb, joined Simona Halep (2), Agnieszka Radwanska (4), Angelique Kerber (6) and Ana Ivanovic (8) in leaving the competition early. Five of the top 10 seeds in the women’s singles have lost.

The US Open women’s draw was blown wide open by a series of upsets on Friday, but it was business as usual on the men’s side with Roger Federer leading a parade of seeds into the third round at the year’s final Grand Slam.

The tremors continued at the US National Tennis Centre as Swiss teen Belinda Bencic ousted sixth-seeded German Angelique Kerber 6-1, 7-5 to reach the round-of-16 in her US Open debut.

By the time fifth seed Maria Sharapova had closed out the action under the Arthur Ashe Stadium floodlights with a laboured 6-2, 6-4 win over Germany’s Sabine Lisicki the top of the women’s draw had lost four of the top eight seeds.

The top 10 men’s seeds, however, remain intact.

Federer, Spanish fourth seed David Ferrer, sixth-seeded Czech Tomas Berdych and seventh-seeded Bulgarian Grigor Dimitrov all advanced on Friday. The highest-ranked casualty was Ernests Gulbis of Latvia, the 11th seed, who was ousted by 45th-ranked Dominic Thiem of Austria 4-6, 3-6, 6-4, 6-3, 6-3.

Federer, chasing an 18th Grand Slam title, served up a tidy 6-4, 6-4, 6-4 win over big-hitting Australian Sam Groth to ease into the third round.

The former world No. 1 has feasted on Australian opponents in Grand Slams over the years, piling up an 18-1 record against men from Down Under, and Groth, who was facing a top 10 opponent for the first time, proved little more than a distraction to the Swiss maestro.

Throughout the one hour and 48 minutes contest, the Australian took his best shots at the 33-year-old, including booming serves of over 140mph. “The 142, honestly I hit it and I turned around,” said Federer. “I didn’t know if it went into the stands or the bottom of the net or on the other side. I just felt like I hit it clean.

“The 147 one I felt like I was there and felt like I had more control on it. The difference between 142 and 147, there’s none really in the racquet. I think once you pass the 135 range everything is just really fast.”

Dimitrov breezed into the third round with a 6-1, 6-2, 6-2 win over Israel’s Dudi Sela. Berdych had a much tougher time, needing five sets and three hours 45 minutes to tame Martin Klizan of Slovakia 6-3, 4-6, 6-2, 3-6, 6-3.

Richard Gasquet, seeded 12th, and Gael Monfils, 20th, advanced in straight sets to set up an all-French collision for a berth in the fourth round.

Working harder was 18th-seeded South African Kevin Anderson, a four-set winner against Jerzy Janowicz of Poland, while Spain’s 19th seed Feliciano Lopez won a fourth-set tie-breaker to advance past Japanese qualifier Tatsuma Ito.

Veteran Indian star Leander Paes and Czech partner Radek Stepanek entered the men’s doubles pre-quarter finals with a straight-set victory in the second round. The sixth seeded pairing defeated Chinese Taipei’s Yen Hsun-Lu and Czech Republic’s Jiri Vesley 7-6 (7-3), 6-3 in a contest which lasted an hour and 23 minutes.

In the intensely contested opening set, both the teams exchanged a break of serve and were guilty of committing an equal number of unforced errors. Lu and Vesley, however, gave away easy points by committing as many as four double faults, eventually falling short in the tie-breaker.

But Paes and Stepanek dominated the second set, clinching two break points and being distinctly better on their second serve. The sixth seeds will next take on the winners of the match between 11th-seeded Spanish pair of Marcel Granollers and Marc Lopez and the Dutch team of Robin Haase and Igor Sisling.

In the junior girls’ competition, Ojasvinee Singh entered the second round of qualifiers after beating local favourite Alexandra Sanford 6-3, 6-2. (Agencies)