Azarekna advances to quarterfinals at Brisbane International

BRISBANE, Australia (AP) After two injury-interrupted seasons, Victoria Azarenka is emerging from the shadows of some her highly-ranked rivals who have either withdrawn from Australian Open warmup events or lost in the early rounds.

The two-time Australian Open champion reached the quarterfinals of the Brisbane International – a tournament she won in 2009 – with a 6-3, 6-2 win over Ysaline Bonaventure on Wednesday.

Bonaventure, a lucky loser from qualifying, was cast into the second round as a replacement for top-seeded Simona Halep, who had a bye before withdrawing from a scheduled second-round match with Azarenka because of an Achilles tendon problem.

The No. 2-ranked Halep announced her withdrawal within an hour of defending champion Maria Sharapova pulling out of the tournament with a left forearm injury. Top-ranked Serena Williams skipped her first Hopman Cup match in Perth and then retired in the second set of the U.S. team's second match, citing inflammation in her left knee. Venus Williams and Ana Ivanovic – the top two seeds at the ASB Classic in Auckland, New Zealand – were ousted in the first round.

Meanwhile, Azarenka, who dropped to a year-end No. 22 ranking in December after being restricted to just 23 events across 2014 and '15, is working her way back into form.

Against Bonaventure, she conceded an early service break and had seven double-faults in the first set, but otherwise dominated after converting her fifth breakpoint chance in a fourth game that lasted more than 17 minutes and went to deuce 11 times.

Fourth-seeded Angelique Kerber and fellow German Andrea Petkovic advanced to the quarterfinals with straight sets wins.

Kerber beat Madison Brengle 6-3, 6-0 to set up a meeting with Anastasia Pavlyuchenkova, while Petkovic had a 7-5, 6-4 win over Ekaterina Makarova to move into a quarterfinal against U.S. qualifier Samantha Crawford, who had an upset 7-5, 7-5 win over seventh-seeded Belinda Bencic.

Petkovic, who has struggled in the past with serious injuries, attributed the high attrition rate in January to the extra work players are putting into the conditioning over the off-season.

''It's maybe just bad luck sometimes and it's a coincidence that all the top players are injured now or struggling, I don't know,'' Petkovic said. ''Also if you play only one tournament before the Australian Open you are extra precautionary I guess compared with other tournaments maybe where you play through with a little pain.

''If I know them well, the top players, they still will be in good shape when it comes to the Australian Open.''

On the men's side, second-seeded Kei Nishikori advanced to the quarterfinals with a 6-3, 6-4 win over Mikhail Kukushkin in his first competitive outing of the season in Australia.

He'll be aiming to reach the semifinals in Brisbane for the fourth straight year with a win over either Bernard Tomic or Radek Stepanek in his next match.

Eighth-seeded Dominic Thiem advanced to the quarterfinals with a 6-3, 6-2 win over Denis Kudla.

In Auckland, Austrian qualifier Tamira Paszek continued her strong run by beating two-time Grand Slam champion Svetlana Kuznetsova to follow up a victory over former French Open champion Francesca Schiavone in the first round.

Former No.1 and third-seeded Caroline Wozniacki is the top player remaining in the main draw.