Serb Olga Danilovic, the top seed, moved into the quarter-finals of the Megasaray Hotels Open 2 when Croat Jana Fett retired on Thursday.
Danilovic, ranked No 41, led 6-0 when Fett, ranked No 134, pulled out of the second round match.
The Serb will face the winner of the match between Swiss Simona Waltert and Sara Bejlek next.
Danilovic defeated Latvian wildcard Adelina Lachinova (6-1, 6-3) ahead of her win today.
In the previous round, the Croat won against Russian wildcard Anastasiia Gureva (6-1, 6-1).
