MELBOURNE (Reuters) - Top seeds Novak Djokovic and Serena Williams barely moved out of second gear while Victoria Azarenka underlined her Australian Open pedigree as players experienced the hottest conditions of the championship so far on Thursday.
Four-times champion Djokovic only needed to up his game after an hour of his 6-0 6-1 6-4 victory over Andrey Kuznetsov, while Williams had to be on her mettle a little sooner following some early resistance from former world number two Vera Zvonareva.
Once the 18-times grand slam singles champion got up to speed, however, she cruised away from the Russian with a 7-5 6-0 victory during the day session.
"Things really clicked. I had no other option but for things to click," the American told reporters as she moved into the third round and within sight of a potential quarter-final with Azarenka.
Twice champion Azarenka, whose ranking has plummeted to 44 after she was restricted to just nine tournaments last year with foot and knee injuries, proved she would not be kept down for long as she hammered eighth seed Caroline Wozniacki 6-4 6-2.
"I knew that I'm unseeded so I can play anybody. I just accept whoever is on the opposite side (and) I'm happy with the way I stayed consistent throughout the whole match," she said.
"I think there's always things you can improve, but it's a great progress from one match to another."
Woziniacki, a former world number one, said while losing "sucks" she felt her good friend was back to her best already.
"Her level, it's high," she said. "I think she's at the level that she left when she stopped playing."
Men's champion Stan Wawrinka, who beat Romanian qualifier Marius Copil, the lowest ranked men's player in the second round at 194, and eighth seed Milos Raonic, who dispatched American Donald Young, also both advanced after clinical victories.
Air temperatures had dropped considerably for the later matches at Melbourne Park, but had exceeded 35 Celsius during the day session, with France's Adrian Mannarino a notable casualty.
The 26-year-old held two match points in the third set against 12th-seed Feliciano Lopez before he was forced to retire while trailing in the fourth.
Lopez was awarded the match 4-6 4-6 7-6(3) 4-0 and will now face Poland's Jerzy Janowicz, who beat 17th-seed Gael Monfils in an entertaining five setter.
Controversy also raged on Thursday after a male television interviewer had asked seventh seed Eugenie Bouchard to showcase her dress with a 'twirl' after her second round victory on Wednesday.
The Canadian later said it was strange to be asked to do such a thing, while social and mainstream media went into overdrive with accusations of sexism, though Williams said there were more important things to discuss.
"I wouldn't ask Rafa (Nadal) or Roger (Federer) to twirl. Whether it's sexist or not, I don't know," she said.
"Life is far too short to focus on that. We have so many other problems we want to deal with that we should focus on."
Williams's victory came about 90 minutes after older sister Venus hammered American compatriot Lauren Davis 6-2 6-3, while sixth seed Radwanska also made short work of Sweden's Johanna Larsson in a 6-0 6-1 victory that took just 44 minutes.
Twice Wimbledon champion Petra Kvitova also advanced after a comfortable 6-2 6-4 victory over Germany's Mona Barthel.
U.S. Open finalist Kei Nishikori was forced to dig himself out of a small hole when he lost the first set to Ivan Dodig, but once he got warmed up, and the temperatures continued to rise, the Croatian wilted.
"It was ... hot out there," Nishikori said after winning 4-6 7-5 6-2 7-6(0). "A lot of sun. It wasn't easy. I was a little bit dizzy and tired.
"But it's going to be like this in Australia."
Editing by Patrick Johnston and Toby Davis