Roberta Vinci reached the quarter-finals of the Istanbul Cup following her victory over Alexandra Dulgheru on Thursday.
Vinci was made to work hard to win the first set and Dulgheru would unfortunately be forced to retire through injury with the scoreboard reading 6-3 4-1 in favour of the Italian.
The world number 24 broke Dulgheru three times in the opening set and would need three set points to secure it.
The short second set saw Vinci race to a 3-1 lead but it was clear that Dulgheru was struggling.
Japanese sixth seed Kurumi Nara needed almost three hours to defeat qualifier Katerina Siniakova 7-6 (7/5) 6-7 (3/7) 6-2 and next meets second seed Vinci.
Croatian teenager Ana Konjuh reached the first WTA Tour quarter-final of her career with a hard-fought victory over Misaki Doi.
The 16-year-old has been rising fast and made the third round of Wimbledon as a qualifier, and she came out on top in a 6-4 6-7 (3/7) 6-4 battle with Doi that took two hours and 15 minutes.
Eighth seed Karolina Pliskova will play top seed Caroline Wozniacki in the last eight after a 6-2 7-5 win over Shahar Peer.