MELBOURNE, Australia – Defending champion Victoria Azarenka struggled to hold off injured American Jamie Hampton 6-4, 4-6, 6-2 on Saturday before advancing to the fourth round of the Australian Open.

Hampton needed a medical timeout for a lower back problem before she served out the second set. She winced in pain, frequently on the verge of tears, throughout the third, but still managed to hit 41 winners to keep the top-ranked Azarenka under pressure.

Azarenka overcame an early break and fended off triple break point in the seventh game of the deciding set before clinching the match in 2 hours, 9 minutes.