MELBOURNE, Jan. 18 (Xinhua) -- Seven-time Grand Slam winner Venus Williams was unable to stop Maria Sharapova here on Friday as the Russian powered into the fourth round of the Australian Open, while men's defending champion Novak Djokovic kept on showing his great status.
Second-seeded Sharapova, who won her first two matches in the Melbourne Park without dropping a game, beat Williams 6-1, 6-3 in an unexpectedly lopsided third-round result.
A forehand winner in the opening game handed Sharapova a break and a further break helped her establish a 4-0 advantage before Williams finally got on the board, which ended Sharapova's run of successive games to start the tournament at 28 games to none.
Then the Australian Open winner in 2008 marched on to break the American's serve for a third time to take the first set.
Sharapova swiftly moved into a 3-0 lead in the second but the 32-year-old Williams continued to fight on. She held off three break points in the fourth game, hitting back from 0-40 to take the game with a blistering forehand down the line.
Sharapova then broke for 5-1 at the fourth attempt but she could not serve it out as Williams fought to break her serve for the first time.
But the 25th seed still could not repeat the feat when runner- up of 2012 served again at 5-3.
Djokovic beat Radek Stepanek of Czech Republic 6-4, 6-3, 7-5 to win his 17th straight match at the Australian Open. The Serbian came through his first serious test of the event by breaking Stepanek's serve in the 11th game of the third set then held to win the match in two hours and 22 minutes.
Djokovic, the two-time defending champion at Melbourne Park who also won the title in 2008, is aiming to become the first man in the Open era to win three consecutive Australian Open title.
Sixth-seeded Chinese Li Na also advanced to the fourth round with a 6-4, 6-1 win over Sorana Cirstea of Romania. It is the consecutive fourth time for the 2011 runner-up to reach the fourth round at the Australian Open.
Li's next-round opponent will be Germany's 18th seed Julia Goerges, who beat Chinese Zheng Jie 6-3, 1-6 and 7-5.
Both players played their best tennis in the deciding set, with powerful strokes coming from both ends of the court. But it was Zheng who made the crucial breakthrough, allowing her to serve for the match at 5-4.
However, Goerges dug deep and broke back to keep her tournament alive. After holding serve, Goerges earned three match points and needed only one to set up a counter with Li Na.
As Li's potential quarterfinal opponent, fourth-seeded Angieszka Radwanska won her 12th match in a row with a 6-3, 6-1 victory over Britain's Heather Waston.