Roger Federer was made to work by 200th-ranked Noah Rubin at the Australian Open on Wednesday -- and it was no cakewalk for birthday girl Angelique Kerber either.

In what could be ominous signs for Federer, America's Rubin kept him largely at bay in the first set and broke in the third, before the 35-year-old won it 7-5, 6-3, 7-6 (7/3).

The 17th seed and 17-time Grand Slam champion, feeling his way back from injury, will face a much tougher assignment in the third round against old rival Tomas Berdych.

"That's not an easy draw," Federer said of Berdych. "He's beaten me at New York and he's beaten me at Wimbledon too, and the Olympics.

"He would like to beat me here. Maybe he has already and I've forgotten."

He wasn't the only leading player challenged in the second round as Kerber, the women's top seed and defending champion, dropped a set against world number 89 Carina Witthoeft.

Kerber 'double-bagelled' Witthoeft two years ago at Wimbledon, but she was extended by her fellow German in her 6-2, 6-7 (3/7), 6-2 win.

The match ended on a light note as Kerber, who turned 29 on Wednesday, was treated to a rendition of "Happy Birthday" by the Rod Laver Arena crowd.

"I was doing I think a lot of mistakes in the important moments. But at the end, I'm happy that I won the match," said the world number one.

Kerber joined Venus Williams and Svetlana Kuznetsova in round three as the Grand Slam-winning veterans enjoyed smoother progress in sunny conditions on day three.

- 'Zero, like zero' -

In the men's draw, Japanese fifth seed Kei Nishikori marched into the third round alongside former finalist Jo-Wilfried Tsonga, with both winning in straight sets.

Nishikori was extended to five sets in his first-round win over Andrey Kuznetsov, but he found the going a little easier in his 6-3, 6-4, 6-3 victory against Jeremy Chardy.

However, he said he hadn't completely clicked into gear, complaining of "up and down" form after he was broken three times by the 72nd-ranked Frenchman.

"It was too much up and down, too many service breaks for me, but it's great to win in straight sets," said Nishikori, who had his serve broken three times by Chardy.

Nishikori, who believes he is due a first major win this year, next plays either Lukas Llacko or Dudi Sela, with Berdych or Federer awaiting in the fourth round.

France's Tsonga, who is seeded 12th and was runner-up to Novak Djokovic in 2008, beat Serbia's Dusan Lajovic 6-2, 6-2, 6-3 to go through.

Stan Wawrinka, the 2014 winner, recovered from his tetchy five-setter with Martin Klizan to beat Steve Johnson 6-3, 6-4, 6-4.

In the women's draw, 36-year-old Williams continued her smooth progress when she beat qualifier Stefanie Voegele 6-3, 6-2 to set up a meeting with China's Duan Yingying.

"I don't know anything about her. I have never seen her play. Zero, like zero," Williams said of Duan.

Williams, the oldest player in the women's draw, pulled out of the doubles competition with her sister Serena as a precaution to rest a sore elbow.

Russia's Kuznetsova thrashed Australian wildcard Jaimee Fourlis 6-2, 6-1 to set up a third-round clash with 31-year-old Serb Jelena Jankovic.

Source: AFP