Samantha Stosur and Zhang Shuai upset the top women's doubles seeds Barbora Krejcikova and Katerina Siniakova 7-6 (2), 7-6 (4) on Tuesday to reach the Australian Open semi-finals. Krejcikova and Siniakova won the French Open and Wimbledon doubles titles last year and reached the semi-finals at the U.S. Open to finish 2018 with the No. 1 ranking. Stosur, who had a career high No. 4 ranking in singles and won 2011 U.S. Open title, has two major women's doubles titles but lost the only final she reached at Melbourne Park in 2006. In another quarter-final upset, Americans Alison Riske and Jennifer Brady knocked out Taiwan's Chan sisters, Latisha and Hao-Ching Chan (7) 6-3, 7-6 to advance, while the Czech pair of Barbora Strycova and Marketa Vondrousova defeated fifth-seeded Andreja Klepac and Maria Jose Martinez Sanchez 6-4, 6-4.