Veronika Kudermetova saved five match points as she beat Danielle Collins to reach the Adelaide International 2 semi-finals before Belinda Bencic knocked Caroline Garcia out.
Sixth seed Kudermetova showed great defiance to defeat American Collins 4-6 7-6 (7-5) 6-1 on Thursday.
Kudermetova fended off five match points when serving to stay in the tournament at 6-5 down in the second set and duly forced a tie-break.
Collins, runner-up to Ash Barty in the Australian Open final last year, took a 3-0 lead in the breaker, but back came her Russian opponent to level the match.
The world number nine dominated the deciding set to seal a meeting with Bencic in the last four.
Eighth seed Bencic got the better of WTA Finals champion Garcia 6-2 3-6 6-4.
Garcia broke straight back after going 3-1 down in the final set, but Bencic broke for the fourth time in the match to go through.
Paula Badosa and Daria Kasatkina will contest the other semi-final after beating Beatriz Haddad Maia and Petra Kvitova respectively.
Elisabetta Cocciaretto saved two match points as she came from a set down to beat Bernarda Pera 5-7 7-6 (10-8) 6-4 in the quarter-finals of the Hobart International.
The 21-year-old Italian will now face 2020 Australian Open champion Sofia Kenin, who also stormed back to defeat Anhelina Kalinina 4-6 6-3 6-1.
Lauren Davis and Anna Blinkova will do battle in the other semi-final following wins over Wang Xinyu and Yulia Putintseva respectively.