Defending champion Victoria Azarenka has withstood a brave challenge from injured American Jamie Hampton to win their third-round clash at the Australian Open.
Hampton, who has a history of back trouble, took a five-minute timeout late in the second set for treatment on her lower back.
Still in obvious pain, the world No.63 was able to clinch the second set before world No.1 Azarenka steadied to win 6-4 4-6 6-2 in a match which lasted for two hours and nine minutes.
Hampton, 22, was also treated for cramp in her legs during the third set to the annoyance of her Belarussian opponent.
The American's last chance came in the seventh game of the final set when she got to 0-40 on Azarenka's serve, only for the top seed to win five straight points and hold for 5-2.
"She played incredible," Azarenka said of Hampton.
"She went for every single shot and I felt like they were touching every single line.
"It was unbelievable."
Hampton was at least able to finish the match, unlike at last year's French Open, when she was forced to withdraw midway through her round-one encounter with Dutchwoman Arantxa Rus due to a back injury.
Azarenka will play either No.16 seed Roberta Vinci from Italy or Russian Elena Vesnina in the round of 16 at Melbourne Park.
In other third-round action early on Saturday, No.14 seed Maria Kirilenko from Russia ousted Belgian No.20 seed Yanina Wickmayer 7-6 (7-4) 6-3.
Fellow Russian Svetlana Kuznestova needed three sets to put away the challenge of Spain's Carla Suarez Navarro 6-2 4-6 6-3.