If Rafael Nadal is getting nervous as he eases closer to winning his fourth consecutive Grand Slam, he sure isn't showing it at the Australian Open in Melbourne.

After his 6-2, 6-1, 6-1 win yesterday over American qualifier Ryan Sweeting, the Spanish star appeared as comfortable talking about his next match - against 18-year-old Australian Bernard Tomic - as he was in beating Sweeting so convincingly.

"Practice a little bit tomorrow, rest in the hotel, maybe going to the aquarium - I go every year. Nothing different," Nadal said, when asked about his preparations for Saturday's match.

Shrugging his shoulders and smiling, he added: "If I start getting nervous two days before a match, I have a big problem."

Nadal hasn't had any real problems in recent Grand Slams - yesterday's win was his 23rd in a row in majors going back to the first round of the French Open last year. Since then, he's carted back to his home in Majorca trophies from Roland Garros, Wimbledon and the US Open.

A fourth from the Australian Open - the Norman Brookes Challenge Cup that he won in 2009 - would make him the first man since Rod Laver in 1969 to hold all four major titles at once.

He's off to an impressive start at Melbourne Park, conceding only four games in two matches, although his opener against Marcos Daniel was cut short when the Brazilian had to retire with a knee injury trailing 6-0, 5-0.

On the women's side, second-seeded Vera Zvonareva overcame a shaky start to beat Bojana Jovanovski of Serbia 2-6, 6-3, 6-1.

Joining her in the third round from the bottom half of the draw were No. 10 Shahar Peer, who beat Sorana Cirstea 6-3, 6-2, and No. 22 Flavia Pennetta.

China's Peng Shuai produced the day's biggest upset, knocking off seventh-seeded Jelena Jankovic 7-6 (3), 6-3. It was former world No. 1 Jankovic's worst result at a major since the 2009 US Open.

Peng said it took some time to get comfortable in the match.

"I felt tight at first," the 25-year-old Peng said. "But as the match went on I realized there were chances for me, so I devoted myself fully to each point."

Also, 12th-seeded Agnieszka Radwanska of Poland beat Petra Martic of Croatia 6-3, 6-4, and 13th-seeded Petrova defeated Australian Alicia Molik 6-4, 6-1.

In men's action, fourth-seeded Robin Soderling of Sweden advanced to the third round with a 6-3, 7-6 (1), 6-1 win over Gilles Muller of Luxembourg, as did fifth-seeded Andy Murray, who lost in the finals to Roger Federer last year. Murray used 16 aces to beat Illya Marchenko of Ukraine 6-1, 6-3, 6-3.

"It's good ... a lot of close games," Murray said. "I hit the ball almost better in the tight situations. I'm going to have to get better if I want to do what I did last year."

In the last match of the night, 2006 finalist Marcos Baghdatis advanced with a 6-1, 6-3, 4-6, 6-3 win over 2009 US Open champion Juan Martin del Potro, who called the trainer on three straight changes of end in the second set to have his problem right wrist treated. Del Potro played only three tournaments last year due to the wrist injury.

Argentina's David Nalbandian, who beat former No. 1 Lleyton Hewitt in a five-set match on Tuesday, retired from his second-round match against Richard Berankis of Lithuania due to exhaustion. Berankis was leading 6-1, 6-0, 2-0.

Asked whether Hewitt's match had affected him, Nalbandian replied, "A lot."

"It was everything, nothing specific," he said. "I toss a ball for the serve and everything was moving around. I called the doctor and he told me that it was dangerous playing like that."

Other seeded players advancing in the men's draw were No. 10 Mikhail Youzhny, No. 13 Jo-Wilfried Tsonga, No. 15 Marin Cilic and No. 32 Guillermo Garcia-Lopez.