(Photo credit: Aaron Doster-Imagn Images)

Coco Gauff and Christian Harrison rallied from a set down to defeat Greece's Stefanos Tsitsipas and Maria Sakkari on Wednesday, sending the United States to the United Cup semifinals in Australia.

Competing in Perth, the Americans finished a 4-6, 6-4, 10-8 mixed-doubles thriller on their third match point.

Gauff had given her team the lead with a 6-3, 6-2 win over Sakkari before Tsitsipas responded with a 6-4, 7-5 win against Taylor Fritz.

Seeking its third United Cup title in four years, the U.S. will play the winner of the Poland-Australia quarterfinal in Sydney. Switzerland will face Belgium or Czechia in the other semifinal.

Switzerland advanced Wednesday with a 2-1 victory against Argentina. Jakub Paul and Belinda Bencic beat Maria Lourdes Carle and Guido Andreozzi 6-3, 6-3 in the decisive match. Bencic defeated Solana Sierra in straight sets and Argentina's Sebastian Baez took down Stan Wawrinka in the singles matches.

Brisbane International

Top-seeded Daniil Medvedev of Russia rolled into the quarterfinals with a 6-3, 6-2 win over Frances Tiafoe in just 60 minutes in Australia.

Medvedev fired nine aces, won 91% of the points (31 of 34) on his first serve and never faced a break point. Up next is Poland's Kamil Machrzak, who weathered a whopping 44 aces from Reilly Opelka in a 6-7 (2), 7-6 (7), 7-6 (8) win that lasted for two-and-a-half hours.

Sebastian Korda was leading 6-3, 1-2 when third-seeded Czech Jiri Lehecka retired. Korda's quarterfinal opponent is fellow American Alex Michelsen, who ousted eighth-seeded compatriot Learner Tien 6-4, 6-2.

Hong Kong Tennis Open

No. 1 seed Lorenzo Musetti rallied to reach the quarterfinals with a 6-7 (3), 6-2, 6-4 victory against Argentina's Tomas Martin Etcheverry.

Musetti converted five of eight break points and finished with a 34-28 edge in winners. He next faces local favorite Chak Lam Coleman Wong, who pulled off a 1-6, 7-5, 7-5 upset of No. 6 seed Gabriel Diallo of Canada.

Third-seeded Russian Andrey Rublev avoided the upset with a 3-6, 6-2, 6-1 comeback against China's Yibing Wu. His quarterfinal opponent will be eighth-seeded Nuno Borges of Portugal, a 7-5, 6-3 winner over Croatia's Marin Cilic.

--Field Level Media