Photos:Sharapova eclipses Venus, Djokovic cruises

Maria Sharapova missed out on a third successive 'double-bagel' but humbled Venus Williams 6-1, 6-3 to charge into the fourth round of the Australian Open on Friday.

The centre court crowd was left stunned as the second seeded Russian scorched to a 4-0 lead in the first set to rattle her American opponent, and charged on in the second to wrap up the match in 79 minutes on a chilly evening at Rod Laver Arena.

The 25th seed Williams sparked raucous cheers by breaking Sharapova and holding her serve late in the second set, but the Russian sealed the match with an ace and unleashed a fist-pumping shriek.

Sharapova will next play Belgian Kirsten Flipkens as she continues her bid for a fifth grand slam title and second at Melbourne Park.

Ana Ivanovic beat fellow Serb and once fierce rival Jelena Jankovic 7-5, 6-3 in a battle of former World No. 1s to reach the fourth round of the Australian Open on Friday.

Three years ago or so, a clash between the two would have been in deep into the latter stages of a Grand Slam, rather than a third-round meeting.

Former French Open champion Ivanovic is seeded 13th this year and Jankovic at 22 but despite their fall from the top of the women's game, their rivalry remains intense.

"It's competitiveness, said Ivanovic, who will next face fourth seed Agnieszka Radwanska after the Pole took her winning streak to 12 matches by thrashing Britain's Heather Watson.

"You have that with everyone you play -- and especially someone coming from your country. We were (once) both looking for the number one position and to win a Grand Slam.

"Of course there is going to be rivalry, but I think there is healthy rivalry too because you kind of push each other.

"We played in the 2008 French Open (semi-finals) and then here we were both in the semi-finals in 2008, so it definitely brings a lot of memories.

"We haven't played each other in a grand slam for a while, but it's always tough.

"She's still a very good player and even though we are different opponents now than we were then, still it's a battle, and every match you want to win."

There was a time where the two would barely exchange a word but over the years their relationship has thawed, also helped by their efforts together in the Fed Cup.

"We had a really good week in Prague for the final of the Fed Cup," said Ivanovic. "We were hanging out a lot, joking. It's nice. We have known each other for a while."

Ivanovic has lost some weight in recent months and says she is still trying to strike the right balance between fleetness of foot and power.

"It's just about the muscle and just getting the right balance because still you need to feel light on the court but you have to be powerful," she said.

"I had a really tough match the other day and today I came out and I was feeling fine and was explosive - so I'm very, very pleased that it's paying off. But I'm still working at it."

Agnieszka Radwanska smiled, laughed and then dismissed any notions of superstition after she advanced to the fourth round.

The 23-year-old Pole had earlier romped to a 6-3, 6-1 victory over Britain's Heather Watson in the third round, notching her 12th successive victory in 2013.

"There is," she said when asked if 13 was considered an unlucky number in Poland as she looked ahead to her fourth round clash with Serbian 13th seed Ana Ivanovic.

"I didn't say that," she hastily added with a beaming smile as if to banish any potential misfortune she may have brought upon herself.

The World No. 4, who could also win her 13th career title if she goes on to lift the Daphne Akhurst Memorial Trophy, was also quick to point out that she was "not actually" superstitious.

Radwanska, who won the Auckland and Sydney titles before the Australian Open and said earlier she "hoped" she was not in the form of her life, added she could not think of a better run of victories and felt she was building nicely into the tournament.

"I think it was a good start," she said of her pre-Australian Open preparations. "Well, I can't complain.

"I really had a lot of good matches against top players this year, and I must say I'm really playing good and everything is working."

Radwanska had little trouble against the 20-year-old Briton, taking advantage of cooler conditions in Melbourne to continue her red-hot start to the year.

American teenager Madison Keys said a new set of headphones for her portable media player was top of her shopping list after bowing out of the Australian Open with winnings of A$54,500 for her third round finish.

China's tempestuous trailblazer Li Na sailed into the fourth round and is poised for a deep run into the second week should she be able to overcome her greatest opponent -- herself.

The sixth seed had little trouble despatching Romania's Sorana Cirstea 6-4, 6-1 on a breezy day at Rod Laver Arena to underline her title credentials in Melbourne.

As shown by her breakthrough French Open triumph in 2011, Li has the game, built around a cracking forehand, to topple the heavyweights if only she can win the mental battle in her head.

A bonus for Li is the absence of four-time Grand Slam champion Kim Clijsters, who beat her in the 2011 final and knocked her out of the fourth round last year.

Li imploded after taking winning positions in both of those matches, but the signs look good at Melbourne Park for the late-blooming 30-year-old, who has now made the second week for a fourth straight year.

"I always try to play my game on the court ... but sometimes I was fighting against myself," the Chinese told reporters.

A welcome wind blew away the stifling heat at Melbourne Park on Friday but there was no diverting Novak Djokovic from his path to a third straight Australian Open title as he marched into the fourth round without giving up a set.

Playing with the roof closed on Rod Laver Arena because of a few drops of rain that accompanied the cooler weather, Djokovic's 6-4, 6-3, 7-5 victory over Radek Stepanek was by no means a cakewalk, however.

The 34-year-old Czech is nobody's mug and the world number one had to work for every point in the 142-minute encounter, getting a good workout, particularly at the net, before sealing the win with a forehand pass.

"Always great to play Radek. He's very experienced, very tricky to play. Hope you enjoyed as much as we did on the court," said 25-year-old Serbian after he reached the fourth round for the seventh year in a row.