She had never played a match against another Russian across the net who bore a strong resemblance to her, physically and in style of play. Her usually reliable serve was getting broken.

Then it all clicked today, and last year's runner-up at the Australian Open was through to the fourth round with a 6-3, 6-0 victory over Elena Vesnina that was a lot harder than the score indicated.

Defending champion Serena Williams and top-ranked Justine Henin also advanced against opponents with similar games. Williams next faces 12th-seeded Nicole Vaidisova, while Henin puts her 31-match winning streak on the line against Taiwanese qualifier Hsieh Su-Wei.

On the men's side, second-ranked Rafael Nadal and No. 4 Nikolai Davydenko advanced in straight sets, while No. 6 Andy Roddick played in the late match against No. 29 Philipp Kohlschreiber.

Nadal next plays No. 23 Paul-Henri Matthieu, who had a five-set victory over Stefan Koubek, while Daveydenko meets fellow Russian Mikhail Youzhny, who downed No. 20 Ivo Karlovic.

After routing Lindsay Davenport in the last round — a match that Sharapova said she prepared for as if it were a final — she seemed puzzled and frustrated that she couldn't put away Vesnina until she finally put it all together and ran off the last nine games.

"I really tried to keep the intensity I had in the previous match, but that's always difficult," said Sharapova, who next faces another Russian, No. 11 Elena Dementieva, who beat Israel's Shahar Peer. "She came out having not really much to lose."

Sharapova grunted louder and louder and hit harder and harder as she was broken twice in the first set by Vesnina, who was in constant trouble on her own serve. Known for her deliberate routine before she serves, Sharapova also got a warning for taking too much time and double-faulted on the next point.

"When it got close, I felt like I had a huge advantage ... whether that's experience or her being a little tight," Sharapova said. "I still felt like I had the edge in the match."

Finally finding her rhythm, particularly on badly executed drop shots and other softer offerings from Vesnina that turned into little more than target practice, Sharapova had 11 winners to only five unforced errors in the second set, breaking Vesnina for the seventh consecutive time to end the match.

Williams, who improved her record to 26-1 at Melbourne Park since the start of 2003, has said she likes hot weather, and on a warm, muggy day, she was wearing a sweatshirt for her warmups.

It must have helped, because she came out hot, as her sister Venus and their mother applauded at courtside.

With opponent Victoria Azarenka liking a fast pace, there were no high, looping moon balls here, just power tennis. And when it comes to power, Williams may be the best.

Her serve was working particularly well, with 15 aces and a stretch of seven service games in which she yielded only six points.

Williams credited physiotherapy treatment she had on her shoulder before the match.

Azarenka played well, but she never had a serious chance. She had no break points, and every time she made a mistake, Williams capitalized.

"I feel pretty good about where I am," she said. "Hopefully, I'll peak later in the tournament."

Vaidisova, who had set points against Williams in the semifinals last year, knows the challenge she faces.

"Obviously, it doesn't get much tougher than that," "She's a great champion, a great fighter. I'll definitely have to have my 'A' game on."

Henin, the 2004 champion, improved her record in Melbourne to 15-1 since '04. She and Schiavone kept each other on the run constantly, mixing up speed and spins to keep each other off-balance.

"She's always given me trouble in the past, so it was a tough third round for me," Henin said.