Top seed Bianca Andreescu battled her way into the quarter-finals of the Strasbourg International then promptly announced her withdrawal from the competition due to injury.
The former US Open champion beat qualifier Maryna Zanevska 6-1 6-4 but opted for a precautionary approach heading towards the imminent French Open in Paris.
Andreescu said in a post-match interview: “I’m super happy with the win today. I will be pulling out of my next match, because I did feel a little bit of an ab tear and I don’t want to push it at all for Roland Garros.”
The other last-16 clash on Tuesday also saw a retirement, with Alize Cornet pulling out of her match against Poland’s eighth seed Magda Linette due to a right hip injury when trailing 7-6 (2) 3-0.
In first-round action, second seed Jennifer Pegula crashed out of the tournament in a 6-4 6-4 defeat to Arantxa Rus, who will next play wild card Harmony Tan, a 6-4 6-4 winner over Alison van Uytvanck.
Shelby Rogers saved a match point before dispatching American compatriot Christina McHale 7-5 6-7 (6) 7-5 in a match lasting almost three and a half hours.
Rogers spurned a match point in the second-set tie-break before McHale missed her chance at 5-4 in the decider. Rogers rallied to clinch a second-round meeting with Jule Niemeier, who beat Diane Parry 6-4 6-3.