MELBOURNE — World No 1 Angelique Kerber got the birthday gift she wanted on Wednesday by making the Australian Open third round, but she had to work hard against fellow German Carina Witthoeft.

The defending champion, who turned 29, battled through 6-2, 6-7 (3/7), 6-2 and will next face either Czech Kristyna Pliskova, sister of fifth seed Karolina Pliskova, or Romanian 27th seed Irina-Camelia Begu.

Venus Williams rolled back the years to move smoothly into the Australian Open third round on Wednesday despite an elbow injury that forced her out of the doubles competition.

The 13th seed, an eight-time quarter-finalist or better in Melbourne, won 6-3, 6-2 against Swiss qualifier Stefanie Voegele, who has never been beyond round two.

Williams, the oldest player in the women’s draw at 36, will next play China’s Duan Yingying, who beat American Varvara Lepchenko.

"I love being here and playing here," said the American veteran. "I played an opponent who didn’t make it easy. It was a battle.

"Today was a good day, a little less hot first thing in the morning, so it was good to get it in, you know, and have a win early."

Williams retired from the warm-up Auckland Classic this month with a sore arm, and she said she was pulling out of the Melbourne doubles with sister Serena as a precaution.

"I’m managing it. I was hoping to have the capacity to play both events here, but at this point I just need to be careful and just try to maintain myself," she said.

The draw has opened up for Williams with fourth seed Simona Halep, whom she was scheduled to meet in the fourth round, already out.

In her 17th Australian Open, the most among active players together with Serena, Williams quickly raced to a 3-0 lead against Voegele, using her powerful groundstrokes to good effect.

But the Swiss 26-year-old was up for a fight on Rod Laver Arena and she broke back with a crisp backhand down the line, then held serve to haul herself back into contention.

Jolted, Williams knuckled down and broke again in the ninth game to comfortably take the set.

It went with serve until the composed seven-time Grand Slam champion seized her opportunity in the fourth game, capitalising on errors to break and go 3-1 in front.

The American, who played her first Australian Open in 1998, was in cruise control and wrapped up the match with a pinpoint backhand in 83 minutes.

She admitted she knew nothing about her next opponent, China’s Duan.

"I have never seen her play. Zero, like zero," she said. "So I’m going to have to see how it goes." — AFP