Australia's Samantha Stosur came through the first real test of her title defense as she beat American Varvara Lepchenko 7-6 6-2 to reach the fourth round on Friday.
The first set was a dogfight but the seventh seed took the tiebreak and then lifted her game to romp through the second set.
Stosur was broken in the opening game of the match, setting the tone for a grueling first set, which lasted 59 minutes.
But the Australian snatched it 7-5 to move ahead and with the pressure off, she ran through the second to reach the last 16.
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