Heather Watson's Olympic preparations suffered a setback as she was beaten by world number 161 Chan Yung-Jan in round two of the Mercury Insurance Open.
The British number one is ranked 90 places above the Taiwanese right-hander, but lost 6-3 7-6 (7-2) at the event in Carlsbad, California.
Watson and Slovak team-mate Janette Husarova play Kai-Chen Chang and Noppawan Lertcheewakarn in the doubles.
won the doubles title
in Stanford last week.
She will partner Laura Robson at the Olympics, while Anne Keothavong and Elena Baltacha represent Team GB in the singles.