Australian Open PHOTOS: Ivanovic upsets Serena; Djokovic Ferrer march into quarters

World No 1 and top seed Serena Williams was knocked out of the Australian Open by Serbian Ana Ivanovic on Sunday.

Ivanovic made her way to the quarter-final after a resounding fight back in the second set to win the fourth round match 4-6, 6-3, 6-3 at the Rod Laver Arena at Melbourne Park.

World No 14 Ivanovic, a former world number one, ended the American's 25-match winning streak to reach her first Grand Slam quarter-final since the 2012 U.S. Open.

Four-time champion Novak Djokovic reached his seventh successive Australian Open quarter-final with a routine 6-3, 6-0, 6-2 victory over 15th-seed Fabio Fognini on Sunday.

The World No 2 needed just 92 minutes to dismantle the Italian, who was having trouble with his serve, struggled to string successive points together and appeared to not be playing to his full ability in the third set.

Djokovic's dominance on return earned him an impressive 22 break opportunities but the Serb was even more accomplished on his own serve, losing just 10 points throughout the entire match as he won a fourth straight contest without dropping a set.

Djokovic's only concern appeared to be with his footing as he slipped over early in the first set, though it did not affect his path to a last-eight encounter against either eighth-seeded Swiss Stanislas Wawrinka or Spain's 17th-seed Tommy Robredo.

Li Na stormed into the quarter-finals of the Australian Open with a 6-2, 6-0 hammering of Russian Ekaterina Makarova in just under an hour on Sunday.

The Chinese fourth seed looked much more assured on Hisense Arena on Sunday and her win set up a last eight meeting with Italy's Flavia Pennetta.

The 31-year-old briskly saved two break points in the first set, another couple at 3-0 up in the second and sealed the win with a backhand volley at the net to serve out to love.

The former French Open champion has a good record at MelbournePark, having reached the final here last year and in 2011 and the semi-finals in 2010.

Italy's Flavia Pennetta advanced to her first Australian Open quarter-final with a 6-1, 4-6, 7-5 victory over ninth-seeded German Angelique Kerber on Sunday.

The 31-year-old Italian could do nothing wrong in the first set, moving Kerber around the court and belting winners from both sides to take it 6-1 in 24 minutes.

Kerber, who lost in the Sydney International final to qualifier Tsvetana Pironkova, took a short break between sets and somehow managed to stay in the match and break the 29th-seed three times to send it to a decider.

Pennetta was broken twice in the third set but rediscovered her rhythm and accuracy to break Kerber three times to advance to her first singles quarter-final at Melbourne Park against either Chinese fourth seed Li Na or Russia's Ekaterina Makarova.

Tomas Berdych trounced Kevin Anderson 6-2, 6-2, 6-3 in a battle of big servers at the Australian Open on Sunday to set up a quarter-final with Spanish hustler David Ferrer.

Berdych, wearing his trademark blue-and-white striped shirt, outgunned Anderson at a rowdy Margaret Court Arena with an impressive array of winners to extend his record to 10-0 over the South African beanpole.

Roared on by a noisy pocket of Czech supporters, the seventh seed sealed his fourth consecutive quarter-final at MelbournePark in just under two hours but will face a far stiffer test against the tireless Ferrer, who delights in dragging opponents into attritional streetfights.

"Probably if I can compare right away all these four years, I think this year is going the best so far," the 28-year-old Czech, a Wimbledon finalist in 2010, said in his courtside interview after blasting 38 winners and breaking Anderson five times.

"There is still a lot of petrol left which I'm definitely going to need in the next match so I'm really happy for that.

"Of course, it's always great to pass the first week, especially the first week here in Melbourne with all the crazy weather.

"It's nice to build up the confidence."

Ferrer also reached the quarter-finals on Sunday for a fourth successive year by overhauling unseeded German Florian Mayer 6-7 (5), 7-5, 6-2, 6-1.

The draw has smiled favourably upon the super-fit 31-year-old, who tends to belt a succession of lower-ranked opponents before being sent crashing out when he faces any one of the 'Big Four'.

Annihilated in last year's semi-finals by triple defending champion Novak Djokovic, Ferrer actually beat Nadal in the 2011 quarter-finals but the 13-times grand slam champion was hampered by injury.

After being dragged into a tiebreak with unseeded Mayer, the Spaniard's superior fitness gradually told and he finished the match full of running, blazing winners from all angles.

"In the third and the fourth (sets), I moved better, I did less mistakes, and I played with power with my shots," Ferrer told reporters after making his ninth consecutive quarter-final in the Grand Slams.

Ferrer boasts a 7-4 winning record over the Czech but was well beaten at the season-ending World Tour championships.

"Of course, Tomas is a top-10 player. Always when I play with him, it's very close," he said.