Defending champion Johanna Konta was bundled out in the first round of the Sydney International by Agnieszka Radwanska and Venus Williams also lost in her first match of the tournament on Tuesday.
Radwanska, overpowered in 82 minutes by Konta in last year's final, raced to a 6-3 7-5 victory over the Briton at the Olympic Tennis Centre.
Neither player was able to dominate on service in the first set and Konta won just two of her 11 second serve points as Radwanska converted three of her five break opportunities.
Konta again had trouble holding serve in the second set but showed signs of a fightback when she broke while trailing 4-1, but she could not push on as Radwanska sealed victory in one hour, 49 minutes.
Second seed Williams was beaten 5-7 6-3 6-1 by Germany's Angelique Kerber in under two hours.
Kerber started the first set stronger and looked to have Williams on the ropes when she opened up a 5-3 lead and created two set points on the American's serve before Williams rallied.
The seven-times grand slam champion survived the Kerber onslaught with an ace and a forehand winner and, with her confidence restored, took the first set.
But Kerber fought back strong as Williams struggled with her service.
The German levelled the match at a set apiece and raced into a 5-0 lead in the decider before Williams rallied again, but the American succumbed to the inevitable on her fifth match point, sending a backhand return wide.
Konta's first-round loss continued some worrying early season performances for the 26-year-old world number nine.
She struggled last week in Brisbane before withdrawing from her quarter-final with a hip injury.
Radwanska, who was upset by American qualifier Sachia Vickery in the Auckland quarter-finals last week, meets American qualifier Catherine Bellis in the second round in Sydney while Kerber faces Dominika Cibulkova in the quarter-finals.
Bartoli looking forward to return to court
Former Wimbledon champion Marion Bartoli just wants to enjoy herself and play big matches when she returns to competitive tennis in March after more than four years in retirement.
The Frenchwoman quit tennis in 2013 weeks after winning her maiden grand slam title at Wimbledon, saying her body could no longer cope with the demands of the sport. She contracted a serious virus last year and feared for her life.
"I let myself get destroyed by someone and I did not think it was possible," Bartoli told French sports daily L'Equipe.
"When I retired, I was the happiest in the world. Then I met my ex boyfriend in May 2014 and everyday he would tell me that I was fat. Every day. He would see a thin girl on the street and tell me: 'See how skinny and pretty she is'."
Bartoli plans to return in March in Miami if she is in shape.
"I want to prove to myself that I am alive. If I come back, it is to try and play big matches on big courts and feel those emotions again," she said.
"I obviously need to lose weight, between five and seven kilos. I will not go back on court if I'm not at my optimum weight."
Bartoli is working hard to be fit.
"When I'm at the CNE (French national tennis centre), I arrive at 9 am and leave at 9 pm. I play tennis between three hour and a half and four hours," she said.
"I am happy to wake up every morning, to be healthy and to have the energy to do the things I want to do during the day."