Canada's Eugenie Bouchard has easily advanced to the third round of the Shenzhen Open in China.
The sixth-seed from Westmount, Que., defeated unseeded American Nicole Gibbs 6-4, 6-2 on Wednesday.
Three seeded players fell by the wayside in second-round play, including third-ranked Irina-Camelia Begu, who retired from her match against Anna-Lena Friedsam of Germany.
Fourth-seed Monica Niculescu of Romania and No. 7 Zarina Diyas of Kazakhstan also lost their matches.
Azarenka rebounds, Serena withdraws
Elsewhere in Australian Open warmup events, Victoria Azarenka is emerging from the shadows of some highly-ranked rivals who have either withdrawn from their tournaments or lost in the early rounds.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.
Bonaventure, a lucky loser from qualifying, was cast into the second round on Wednesday 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 withdrew within an hour of defending champion Maria Sharapova pulling out of the tournament with a left forearm injury. Top-ranked Serena Williams withdrew from the Hopman Cup in Perth after skipping her first match and retiring in the second set of the U.S. team's second against Australia Gold because of inflammation in her left knee.
Venus Williams and Ana Ivanovic — the top two seeded players at the ASB Classic in Auckland, New Zealand — were beaten in the first round.
Azarenka conceded an early service break against Bonaventure and had seven double-faults in the first set, but otherwise dominated after converting her fifth break-point chance in a fourth game that lasted more than 17 minutes and went to deuce 11 times.
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.
"I definitely missed playing since I haven't in a while," she said. As for the broader issue of injuries, she said: "I'm just going to try to take care of myself right now, and hopefully everybody will be ready for the Australian Open."
Fourth-seeded Angelique Kerber beat Madison Brengle 6-3, 6-0 to set up a meeting with Anastasia Pavlyuchenkova, while Andrea Petkovic had a 7-5, 6-4 win over Ekaterina Makarova to move into a quarter-final 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.
"If I know them well, the top players, they still will be in good shape when it comes to the Australian Open," Petkovic said.
In the men's draw, second-seeded Kei Nishikori opened with a 6-3, 6-4 win over Mikhail Kukushkin to move into the quarter-finals against seventh-seeded Bernard Tomic, a 7-6 (6), 4-6, 7-6 (4) winner over Radek Stepanek.
Third-seeded Marin Cilic beat Chung Hyeon 7-5, 7-6 (3), and No. 8 Dominic Thiem had a 6-3, 6-2 win against Denis Kudla to advance.
At the Hopman Cup mixed teams event in Perth, Western Australia, Germany levelled its record at 1-1 with a 2-1 win over France, which lost for the second time.
Alexander Zverev gave Germany a 1-0 lead with a 6-2, 6-2 win over Kenny De Schepper, but Caroline Garcia beat Sabine Lisicki 6-2, 7-6 (5) to send the match to a mixed doubles decider, which the German pair won 6-4, 6-7 (6), 10-6.
In a night match, Andy Murray lost to Australia Green's Nick Kyrgios. Heather Watson was playing Daria Gavrilova in a bid to keep Britain alive.
In New Zealand, third-seeded Caroline Wozniacki resisted the fate of other seeded players at the tournament with a 6-0, 6-2 win against Christina McHale and No. 5 Sloane Stephens beat Carina Witthoeft 3-6, 6-1, 6-3.
Austrian qualifier Tamira Paszek beat two-time Grand Slam champion Svetlana Kuznetsova and British qualifier Naomi Broady reached the quarterfinals with a 4-6, 7-6 (4), 7-5 win over Jelena Ostapenko of Latvia.