Emma Raducanu suffered an injury scare just four days before the French Open begins as the Briton lost to Danielle Collins in Strasbourg.
The 22-year-old produced an excellent first set but needed treatment on a lower back issue after falling 5-0 behind in the second.
Seemingly uninhibited by the problem on her return, Raducanu came back from a break down in the decider - but Collins rallied again to win 4-6 6-1 6-3 and reach the quarter-finals.
Raducanu had taken a wildcard into the clay-court event in Strasbourg to get more practice on the surface before the French Open starts on Sunday.
Despite the off-court medical timeout there appeared to be no obvious signs of discomfort for Raducanu, who put Collins under sustained pressure before the American pulled away.
Collins, a former Australian Open runner-up who beat Roland Garros champion Iga Swiatek in Italy last week, plays American top seed Jessica Pegula or Russian world number 30 Anna Kalinskaya in the last eight.
