MELBOURNE, Australia - Wildcards Astra Sharma and John-Patrick Smith were the toast of last year's Australian Open mixed doubles draw as the home favorites ploughed through a series of more established pairs to reach the final - and they're back for another run this year, moving into the quarterfinals with a 6-3, 4-6, [10-4] upset of No.7 seeds Samantha Stosur and Jean-Julien Rojer.

The Australian duo, who lost the 2019 final to Barbora Krejcikova and Rajeev Ram, impressed with their team synchronicity and sharp serving in coming through a super-tiebreak against Stosur and Rojer. Sharma's groundstrokes were also on song, with the 24-year-old's hammer blows frequently getting the better of her net opponent. Dominating the closing stages, a brilliant Smith lob took his team to match point, whereupon Stosur coughed up a double fault to hand defeat to her compatriots.

Indeed, all three mixed doubles second-round clashes on the Day Eight slate would end in defeat for a seeded pair. Zheng Saisai and Joran Vliegen, the conquerors of Venus Williams and Juan Sebastián Cabal in the first round, saved a match point to eke out No.8 seeds Hsieh Su-Wei and Neal Skupski 3-6, 6-3, [11-9]. Having narrowly led for most of the shootout but fallen behind 8-9, Zheng and Vliegen survived when a Skupski return drifted wide - before Zheng seized control, nailing a high volley and a clean return winner to see her team over the finishing line.

Meanwhile, Iga Swiatek bounced back from the disappointment of narrowly missing out on her maiden Grand Slam quarterfinal in singles to pair up with Polish compatriot Lukasz Kubot for a 6-2, 6-3 upset of No.4 seeds Chan Hao-Ching and Michael Venus in just 62 minutes.