Second-seeded Dominika Cibulkova beat defending champion Anastasia Pavlyuchenkova 7-6 (3), 6-4 to reach her eighth semifinal of the season at the Generali Ladies on Friday.
Cibulkova will next play fourth-seeded Carla Suarez Navarro of Spain, who defeated Denisa Allertova of the Czech Republic 6-4, 4-6, 6-2.
Cibulkova, who won two titles this season and appeared in three more finals, lost a 5-1 lead in the opening set before taking the tiebreaker. The 10th-ranked Slovak also led 5-1 in the second before wrapping up the win on her third match point.
Earlier, Madison Keys advanced to her fifth semifinal of the season by beating Oceane Dodin of France 6-3, 6-3.
The seventh-ranked American will play either top-seeded Garbine Muguruza, the French Open champion, or Viktorija Golubic of Switzerland for a place in Sunday's final.
The third-seeded Keys converted all three of her break points on Dodin's serve and the French qualifier double-faulted on match point.
Keys, who hasn't dropped a set in the tournament, is 3-1 in semifinals this season. She won her second career title in Birmingham in June.