Svetlana Kuznetsova fought back for the second match running to down home favourite Timea Bacsinszky 5-7 6-3 6-4 and punch a ticket to the last eight of the Ladies Open Lugano.
The veteran two-time grand slam champion, playing a first tournament since September, needed three sets to defeat Ekaterina Alexandrova in round one and was taken the distance again by the Swiss in a match held over from Wednesday due to rain.
It could have been a more serene victory had she capitalised on a pair of breaks in the opening set but Bacsinszky rallied to take the advantage and broke again to lead in the second.
However, Kuznetsova won four straight games from 2-1 down before levelling the match and took the only break of a tight decider in game three to reach the quarter-finals.
Stefanie Voegele saw out her contest with Viktorija Golubic 6-1 6-1 having led 3-0 before rain stopped play on Wednesday.
Kristyna Pliskova was a 6-2 6-4 victor over Antonia Lottner, while Vera Lapko, Iga Swiatek and Veronika Kudermetova also progressed to the last eight.