France's Marion Bartoli was swiftly brought back down to earth as she was beaten in her first match since the Wimbledon final.
Bartoli was the second seed in California
The 22-year-old, who has recently recovered from stomach flu, lost 7-5 4-6 3-6 to American Lilia Osterloh at the Stanford Classic.
"My body hasn't recovered from the past two months," said Bartoli, who left the court in tears.
"I had no energy and felt so sick and it cost me in the match."
Osterloh, a former NCAA champion for Stanford University, had the backing of most of the centre court crowd.
"It's a great feeling to beat someone who beat the number one and number three players in the world at Wimbledon. It helps my confidence a lot," the world number 106 said.
Russia's Anna Chakvetadze is the top seed in California. She will face Eleni Daniilidou of Greece in the second round on Thursday.
In Indianapolis on Wednesday, Britain's James Auckland and partner Tripp Phillips narrowly lost their first-round encounter with Scott Lipsky and David Martin 6-4 3-6 8-10.