MELBOURNE, Australia -- Maria Sharapova followed Serena Williams out of the Australian Open in the fourth round, losing 3-6, 6-4, 6-1 to Dominika Cibulkova on Monday in the second major upset in 24 hours on Rod Laver Arena.
Third-seeded Sharapova struggled with her serve starting from the eighth game, when she was broken at love while trying to serve out the first set.
She was broken in four straight games as Cibulkova raced to a 5-0 lead in the second set, during which time Sharapova only won three points on her own serve.
The four-time major winner rallied to win four straight games before Cibulkova held serve to level the match. After taking an off-court medical time out after the second set for what appeared to be a lower back problem, she had seven double-faults in the third set.
Sharapova, who was two tournaments into a comeback from a prolonged layoff with a right shoulder injury, won the Australian title in 2008 and has lost in two other finals at Melbourne Park.
Top-ranked Williams, a five-time Australian Open champion, was knocked out in a three-set loss to 14th-seeded Ana Ivanovic on Sunday, and later revealed she had a back problem that had her considering withdrawing from the tournament.
The absence of two of the biggest stars in women's tennis opens up the draw for two-time defending champion Victoria Azarenka, who was playing No. 13-seeded Sloane Stephens later Monday.
Sharapova made it hard for herself in Australia, having difficulty closing out her second- and third-round matches. She needed almost 3½ hours to beat Karin Knapp in searing heat the second round -- playing 50 minutes between her first and final match points.
Cibulkova had spent just over 3½ hours on court in her first three wins, including a 6-1, 6-0 win over No. 16 Carla Suarez Navarro in the third round.
The pair hadn't played since Sharapova's quarterfinal win at Wimbledon in 2011. Now they're evenly split in six head-to-heads, but Cibulkova has won two of their three matches at the majors with her win Monday and her quarterfinal victory at the 2009 French Open.
Cibulkova raced to a 5-0 lead in the second set before tightening up and letting Sharapova back into the match. She was more steady in the third, when she didn't even face a break point.
"I was never doubting myself," the No. 20-seeded Cibulkova said, adding that Ivanovic's win over Williams the previous day had been motivational but not her main inspiration against Sharapova.
"It was a great match for Ana. But this was a different story. I already beat Maria before and I beat her" at a major.