Hobart, Australia (SportsNetwork.com) - American women Alison Riske and Madison Brengle each won two matches on Thursday to reach the semifinals at the Hobart International tennis event, a final Australian Open tune-up.

The eighth-seeded Riske started her day with a 6-2, 4-6, 6-1 victory over Serb Bojana Jovanovski, while Brengle beat Ukrainian fellow qualifier Kateryna Kozlova 6-1, 7-6 (10-8) in the second round.

In quarterfinal action, the Pittsburgh native Riske then upset second-seeded Kazakhstani Zarina Diyas 6-3, 6-0 and the Delaware native Brengle overcame Italian Karin Knapp 6-7 (3-7), 6-4, 6-4.

Two other quarterfinal results saw Japan's Kurumi Nara upend third-seeded Italian Camila Giorgi 6-1, 3-6, 6-2 and Brit Heather Watson humble ninth- seeded Italian Roberta Vinci 7-6 (7-0), 6-2.

Three other second-round bouts saw Knapp oust top-seeded Aussie Casey Dellacqua 7-5, 2-6, 6-3, Diyas down Slovakian wild card Daniela Hantuchova 7-5, 6-1 and Giorgi receive a walkover past Estonian Kaia Kanepi.

Five second-round matches were postponed because of rain here on Wednesday.

Friday's semifinals will pit Riske against Watson and Brengle versus Nara.

This year's Hobart titlist will earn $43,000.