MELBOURNE, Australia - The wildcard duo of Astra Sharma and John-Patrick Smith thrilled the home crowd by stunning US Open champions Bethanie Mattek-Sands and Jamie Murray 6-2, 7-6(5) in the Australian Open mixed doubles quarterfinals.

Sharma had already caused a stir in Melbourne with her exploits in qualifying and winning a round in the singles main draw, but the former Vanderbilt University college star's dream tournament isn't done yet. The Australians were all over their more accomplished opponents in the first set, smothering Mattek-Sands and Murray with pace and sharp net play and breaking each server once.

A tense, tightly contested second set saw Sharma and Smith edge ahead twice, but get pegged back both times. Powerful Sharma groundstrokes outdid Mattek-Sands at net to capture the Murray serve in the fifth game - but stellar net play and emphatic smashes from the American-British pair to break Smith right back.

In the eleventh game, both Sharma and Smith nailed big returns to break Mattek-Sands - but, serving for the biggest match win of her career, the former lapsed into error to send the set into a tiebreak. But there, they righted the ship, jumping out to a quick 5-1 lead and maintaining the lead to seal victory on their second match point.

"It's unreal, I didn't even expect half of this!" exclaimed Sharma in the on-court interview afterwards, while her partner was overflowing with praise: "It's been a blast - she's awesome to play with and she's got a great future," said Smith.

In the semifinals, Sharma and Smith will face another stern test in No.2 seeds Nicole Melichar and Bruno Soares, who defeated No.6 seeds Abigail Spears and Juan Sebastián Cabal 6-1, 7-6(3). Meanwhile in the top half, María José Martínez Sánchez and Neal Skupski caused another shock by eliminating defending champions and No.1 seeds Gabriela Dabrowski and Mate Pavic in another close contest 6-1, 4-6, [11-9]; the unseeded Spanish-British duo will meet No.3 seeds Barbora Krejcikova and Rajeev Ram in the last four, after the Czech-American pair defeated No.5 seeds Anna-Lena Groenefeld and Robert Farah 6-2, 7-5.