Ekaterina Makarova was responsible for the latest shock at the Australian Open when the Russian knocked out ninth seed Karolina Pliskova in straight sets on Saturday.
Makarova, seeded 21st, beat her opponent from the Czech Republic 6-3, 6-2 in 71 minutes.
Seventh seed Angelique Kerber, meanwhile, advanced to the last 16 when she thumped American Madison Brengle 6-1, 6-3 in another third round match in Melbourne.
Makarova will take on Britain's Johanna Konta while Kerber faces her German compatriot Annika Beck for a place in the quarter-finals.
Beck beat another German player, Laura Siegemund, 6-0, 6-4 in her third round match.
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