Angelique Kerber won her eighth consecutive match of the new season, coming from 3-1 down in the final set to beat qualifier Camila Giorgi 6-2, 6-3 to reach the Sydney International final on Friday.
Kerber, a former No. 1 and the 2016 Australian Open champion, won all four singles at the Hopman Cup and now all four in Sydney en route to the final.
She will face Ashleigh Barty, who beat Australian compatriot Daria Gavrilova 3-6, 6-4, 6-2 in the other semifinal.
In a match that included 11 breaks of serve, Barty needed just one in the third set.
"It's nice getting a bit of confidence going into our biggest tournament for us," Barty said of next week's Australian Open.
Gavrilova's frustration with her serving were evident in the ninth game of the set when, soon after leveling at 4-4, she double-faulted twice and received a code violation for smashing her racket.
In men's semifinals, Russian qualifier Daniil Medvedev booked a spot in the final by upsetting fourth-seeded Fabio Fognini of Italy 2-6, 6-4, 6-1.
Medvedev will next play Australian 18-year-old Alex de Minaur, who defeated Benoit Paire of France 4-6, 6-1, 6-1.
The 167th-ranked de Minaur, who will play his first ATP Tour final on Saturday, advanced to the Brisbane International semifinals last week.