Gavrilova had a tough contest against unseeded American Bernarda Pera with the match playing all three sets in 5-7 7-5 6-3 win.

Despite a promising start from the 24th seed, the errors made outnumbered the winners from both Gavrilova and Pera.

Gavrilova led 5-2 before Pera won seven games in a row to take an advantage but after Pera took the led and a double-break, the Aussie staged a fightback and it brought her level in the second game.

After two hours and 33 minutes, Gavrilova was able to close out the comeback and now faces Belgian 16th seed Elise Mertens.

Stosur saw off doubles teammate Anastasia Pavlyuchenkova 6-2 7-6(1) to set up a third-round meeting with 2016 champion Garbine Muguruza.

It was the 11th time the 34-year-old had made it through to the last 32.

While Stosur fell behind at the start of the first and second sets, she was able to recover and go on to dominate the opener before battling hard to stay in the second.

It came down to a tie-break in the second and Stosur raced into a 6-0 lead before closing it out.