Second-seeded Agnieszka Radwanska defeated a tired Barbora Strycova 6-1, 6-2 on Thursday to advance to the Sydney International final against either Johanna Konta or Eugenie Bouchard.
Radwanska, who will be the third-seeded player at next week's Australian Open behind No. 1 Angelique Kerber and second-ranked Serena Williams, took just 75 minutes to beat Strycova.
It was Radwanska's seventh consecutive win against the Czech, who toiled for 3 hours and 20 minutes to beat Caroline Wozniacki the previous day, than backed that up with a doubles match.
Radwanska has not lost her last six finals.
In men's play at Sydney, Gilles Muller beat second-seeded Pablo Cuevas 7-6 (5), 6-4 to advance to the semifinals against two-time defending champion Viktor Troicki.
Troicki had been scheduled to face No. 5 Philipp Kohlschreiber in another quarterfinal Thursday, but the German withdrew with a back injury, handing third-seeded Troicki a walkover.
Cuevas saved six set points during the first set, including two in the tiebreaker. In the second set, Muller broke Cuevas' serve for a 4-3 lead.
Andrey Kuznetsov also advanced to the last four with a 2-6, 6-4, 6-1 win over fourth-seeded Pablo Carreno Busta.
At the ASB Classic in Auckland, New Zealand, seventh-seeded Steve Johnson beat two-time champion and fellow American John Isner 6-3, 5-7, 7-6 (3).
Johnson gained a vital mini-break on the first point of the tiebreaker but Isner fired down three aces to stay in the contest, only for an unforced error at the net to give Johnson a 6-3 lead. Johnson took the match on his first match point with the help of a net cord.
"Last year I was here and my attitude wasn't the best, but you live and you learn, you come back and I'm glad I turned it around this year," said Johnson, who lost in the first round in 2016.
Eighth-seeded Marcos Baghdatis and unseeded Jaoa Sousa also advanced with straight-set victories. Sousa beat Robin Haase 6-3, 6-2 while Baghdatis defeated 2015 champion Jiri Vesely 6-2, 6-4.
"I've never met him before, but we've practiced a couple of times," Baghdatis said of Sousa. "I know how he plays so I have to focus on what I have to do and try to improve some things, talk with my coach and see what to do."
At the WTA's Hobart International, Elise Mertens had an upset 6-2, 7-5 quarterfinal win over top-seeded Kiki Bertens. Mertens will play Jana Fett, who beat Veronica Cepede Royg 6-1, 6-4, in the semifinals.
Lesia Tsurenko also advanced to the semis with a 6-4, 4-6, 6-3 win over American Shelby Rogers. Tsurenko will next play Japanese qualifier Risa Ozaki or Romania's Monica Niculescu, who played their quarterfinal later Thursday.