Second seed Sloane Stephens was a surprise casualty in the Internationaux de Strasbourg second round as Pauline Parmentier recorded a 6-3 1-6 6-4 win.
A semi-finalist 12 months ago, Stephens was unable to replicate her form as Parmentier put a poor second set behind her to progress.
Parmentier - who has not won a title on the WTA Tour since 2008 - needed three set points before she was able to move ahead, but the momentum quickly deserted her as Stephens roared back into contention.
However, after levelling the match the 23-year-old American struggled to hold her serve in a deciding set that saw both players encounter problems, Parmentier ultimately holding her nerve to reach the last eight.
She will meet Mirjana Lucic-Baroni in the quarter-finals after she also ended the hopes of a seeded player, comfortably beating Timea Babos (8) 6-1 6-4.
There were no such problems for the other seeds in action as Elena Vesnina (7) and Kristina Mladenovic (4) recorded victories, the former ending Kateryna Bondarenko's hopes while the latter came from a set down against Alison Riske.
Also on Wednesday, 2014 champion Monica Puig exited the competition. The Puerto Rican forced to retire in the deciding set against Virginie Razzano with a groin problem.