Third-seeded Maria Sharapova has been defeated in the fourth round of the Australian Open, losing 3-6, 6-4, 6-1 to Dominika Cibulkova in the second major upset in 24 hours on Rod Laver Arena.

Sharapova struggled with her serve on Monday, hitting seven double-faults in the third set, and needed an off-court medical time out after the second set for what appeared to be a lower back problem. The four-time major winner was two tournaments into a comeback from a prolonged layoff with a right shoulder injury.