Anastasia Pavlyuchenkova stuns 11th seed Elina Svitolina, Vandeweghe beats Bouchard in three sets

The Russian 24th seed won the opening set 7-5 before the Ukrainian hit back to level up with a 6-4 win in the second set.

However, Pavlyuchenkova stormed to a 5-2 lead in the decider and finally clinched the victory with a 6-3 score on her fifth match point.

She will now face Svetlana Kuznetsova or Jelena Jankovic - the No 8 seed.

Meanwhile, Coco Vandeweghe rallied from a break down in the deciding set to sweep past Eugenie Bouchard 6-4 3-6 7-5, setting up a potential fourth-round clash against defending champion and world number one Angelique Kerber.

The 26-year-old American, who had never advanced beyond the third round at Melbourne Park before, dominated on serve and needed just the one break opportunity to clinch the first set.

Bouchard, who reached the semi-finals at Melbourne Park three years ago but has seen her ranking tumble after injury and poor form, fought back with a break in the second game of the second set to ensure the match went into a decider.

The Canadian seized an early advantage in the third but the American broke back in the eighth game, staved off four break points in the next and then clinched victory in two hours, 21 minutes with a backhand winner to set up a clash against either Kerber or Kristyna Pliskova.