Number one seed Maria Sharapova had to dig deep to beat Poland's Agnieszka Radwanska 6-2 3-6 6-0 in the quarter-finals of the Istanbul Cup.
Sharapova has been out for two months with the shoulder injury
Sharapova, who seemed to be hampered by her long-running shoulder injury, claimed the opening set but was broken three times as she lost the second.
The Russian fought back in the third but was made to work for every point.
"My shoulder is still aching a little bit and my opponent was really very tough," she said.
Sharapova, who has been out for two months with the shoulder injury, will now take on Aravane Rezai of France in Friday's semi-final.
Rezai, who defeated fourth seed Venus Williams in the second round, reached the last four with a 1-6 6-1 6-4 victory over Meghann Shaughnessy.
In the other semi-final, second seed Elena Dementieva will face fifth seed Alona Bondarenko of the Ukraine.
Dementieva struggled in her quarter-final against Colombia's Catalina Castano but eventually prevailed 1-6 6-4 6-4 while Bondarenko received a bye after Patty Schnyder withdrew because of a thigh injury.