A record-breaking victory by world No.1 Serena Williams has set the standard for top-ranked players on day five of the Australian Open.

Williams’ 6-3 6-3 defeat of Slovakia’s Daniela Hantuchova in their third-round meeting on Friday was the American’s 61st win in her 14 appearances at the championship – one more than Australian legend Margaret Court.

With players desperately seeking to spend as little time on court as possible on another oppressively hot Melbourne day, Williams took 80 minutes to seal her win and then received the not-unwelcome news that an injury to her sister Venus meant their doubles match also scheduled for Friday was cancelled.

“It’s tough mentally and physically but I was prepared,” said Serena, who has dropped only 12 games in her opening three singles matches.

Chinese fourth seed Li Na had to fight harder and endure a lot more heat before claiming victory in her third-round match.

Li admitted to being helpless in the opening set against Czech Lucie Safarova and overcame a match point against her in the second before winning 1-6 7-6 (7-2) 6-3 in two hours and 37 minutes.

“In the first set I couldn’t do anything,” Li said.

“She played very nice and I just had to think about putting the ball back in the court and running.”

Only minutes before Williams scored her landmark victory, German ninth seed Angelique Kerber became the first woman into the fourth round thanks to a straight-sets victory over American Alison Riske.

Kerber said she had to force herself to focus on her game and not the weather.

“I’m just happy to have won and got off the court before it became really hot,” she said.

“I was trying to concentrate on each point and forget about the sun.”

Kerber won 6-3 6-4 to reach the same point in the championship as last year.

Also through in straight sets was Italy’s Flavia Pennetta, the 28th seed accounting for Germany’s Mona Barthel 6-1 7-5.