Sydney - World number two Simona Halep battled an Achilles injury as she overcame France's Caroline Garcia in three sets at the Sydney International on Tuesday.
The Romanian, who was was set to make her 2016 debut at last week's Brisbane International only to pull out with the Achilles injury, downed Garcia 6-4, 2-6, 6-1.
Halep, now coached by Australian Darren Cahill, recovered from a faltering second set to power into the quarter-finals where she will face Czech fifth seed Karolina Pliskova.
"I had pain in the second set. This Achilles pain is coming and going away," Halep said. "So I'm not sure when it's coming and when it's going."
"I have to stay focused, I have to stay patient, and try to stay there in the match and to not think too much about the pain.
"It's tough to play with the pain, because when you have pain you always get scared because you don't know what is going to happen."
Pliskova dropped only three games in beating Russian Anastasia Pavlyuchenkova.
Halep beat Pliskova in both their previous meetings.
German world number seven Angelique Kerber earlier withdrew from the tournament, adding to a lengthy list of ailing women stars ahead of next week's Australian Open in Melbourne.
The fourth seed, who won her first-round match against Ukraine's Elina Svitolina in fierce heat over three sets on Monday, pulled out citing a gastro-intestinal illness.
Her withdrawal follows that of defending champion Petra Kvitova, who also had gastro-intestinal problems, and second seed Agnieszka Radwanska who dropped out with a leg injury.
Kerber, who lost to Victoria Azarenka in Saturday's Brisbane International final, said she experienced problems overnight after Monday's victory.
"I'm very sorry I can't go on court today but I'm not feeling 100 percent," Kerber said.
"I started to feel unwell yesterday and today my stomach is not right. I don't want to risk my health before Melbourne."
The trio's withdrawals came after injury problems at other Australian tournaments for the world's top-ranked stars - including Serena Williams with a knee ailment, Garbine Muguruza who hurt her foot and Maria Sharapova who injured her forearm.
Among other second-round winners Tuesday were Italy's Sara Errani over Jelena Jankovic in two tiebreak sets, Swiss eighth seed Belinda Bencic in straight sets over Bulgarian Tsvetana Pironkova and Australian Samantha Stosur over Slovakian Daniela Hantuchova 6-4, 6-2.
Stosur is through to the quarter-finals in Sydney for the first time since reaching the final in 2005.