Adelaide - World No 7 Belinda Bencic won her first match of the season Monday, but there was agony for Alex de Minaur as the men's top seed pulled out of the Adelaide International In Australia.
The Swiss 22-year-old, a wildcard entry who lost her opening match of the year last week in Shenzhen, beat good friend Daria Kasatkina of Russia 6-4, 6-4.
Three-time Grand Slam champion Angelique Kerber, promoted to ninth seed when Petra Kvitova withdrew, dominated China's Wang Qiang 6-1, 6-3.
Kerber, a former No 1 who took a long three-month off season, won the tournament in 2018 when it was played in Sydney, defeating Ashleigh Barty in the final.
"In the first set I was playing well, but the second was really tight," the 18th-ranked Kerber said.
"This is my first win of the year, I'm happy about that. I hope I can play like today in the next rounds.
"I want to win a few more matches before going to Melbourne," the 2016 Australian Open champion added.
Bencic, who lost her last two matches against the qualifier, overcame hot conditions at Memorial Drive as she makes final preparations for next week's Australian Open.
She survived a first set against Kasatkina featuring five breaks of serve and secured her second-round place with a break in the final game of the second.
"It was very difficult, but I like the heat and I'm happy to be here for the first time," said Bencic, who soared up the rankings last year and won two titles, in Moscow and Dubai, on her way to a career-best 49 main-draw match wins.
"Her game is really tough, it doesn't match up with mine. I had to work hard."
Russia's Anastasia Pavlyuchenkova, American Danielle Collins and Croat Donna Vekic were among other women to clear the first hurdle.
A devastated De Minaur withdrew due to an abdominal injury, casting doubt over his fitness for the first major of the season.
He was the second seed to pull out of the ATP-WTA event after Novak Djokovic opted to head instead to Melbourne to prepare for his title defence at the opening Grand Slam of the year after leading Serbia to the ATP Cup title in Sydney.
"It's devastating. Adelaide has been part of my schedule for a long time," said de Minaur, who had an intense week leading Australia at the ATP Cup teams event.
De Minaur did not mention the Open, which starts on January 20, but gave every indication that he was facing a race to be ready.
"My sole focus is making sure I recover for the next one," added the 18th-ranked player, who helped Australia to the semi-finals at the ATP Cup, winning two of his four singles and pushing world number one Rafael Nadal hard over three sets.
In the men's draw Britain's Dan Evans, also fresh from the ATP Cup, beat Argentinian Juan Ignacio Londero 6-2, 6-4 while Jeremy Chardy overcame fellow Frenchman Gilles Simon 6-3, 7-5.
Australian wild card James Duckworth lined up a match with second seed Felix Auger-Aliassime after defeating Federico Delbonis 6-4, 6-4.
"He's a great young talent, one of the future stars of our game," the Australian said. "I'm going to have to come out and serve well again."
Results on day two of the ATP-WTA Adelaide International at Memorial Drive (x denotes seed):
Jeremy Chardy (FRA) bt Gilles Simon (FRA) 6-3, 7-5
Daniel Evans (GBR) bt Juan Ignacio Londero (ARG) 6-2, 6-4
Lloyd Harris (RSA) bt Christian Garin (CHI x6) 7-6 (7/5), 3-6, 6-4
Sam Querrey (USA) bt Gregoire Barrere (FRA) 6-7 (4/7), 6-2, 7-6 (7/5)
James Duckworth (AUS) bt Federico Del Bonis (ARG) 6-4, 6-4
Anastasia Pavlyuchenkova (RUS) bt Anett Kontaveit (EST) 6-2, 6-4
Belinda Bencic (SUI x4) bt Darya Kasatkina (RUS) 6-4, 6-4
Danielle Collins (USA) bt Aliaksandra Sasnovich (BLR) 6-3, 6-2
Sofia Kenin (USA x7) bt Viktorija Golubic (SUI) 6-0, 6-4
Donna Vekic (CRO) bt Anastasija Sevastova (LAT) 4-6, 6-1, 6-3
Ajla Tomljanovic (AUS) bt Yulia Putintseva (KAZ) 7-6 (7/4), 6-2