In her first competitive outing since withdrawing from the US Open, Bouchard lasted little over a set, saluting the crowd before leaving the court in tears following a lengthy consultation with the trainer.
"I thought I was physically ready but unfortunately the symptoms of my concussion came back," Bouchard said in a statement after the match. "I want to thank all my fans at the China Open for their support. I hope to get well soon and look forward to returning next year."
Bouchard, who was trailing 6-2, 1-1 at the time, last struck a ball in anger during a pulsating third round win over Dominika Cibulkova in New York at the start of September. However, her joy was short lived, a bizarre changing room accident bringing her revival to an abrupt halt.
Early on against Petkovic, there were plenty of signs of rustiness, the Canadian dropping serve from 40-15 in the opening game. The German put the set beyond Bouchard with a break to love in the seventh game before the match's abrupt conclusion.
"I just asked her what happened, and she told me that she felt very dizzy," Petkovic said when asked about Bouchard's retirement. "Then I asked if it was the same, if it was still the concussion. She said it tends to come back when she gets physically very active.
"I feel it's really bad luck because I thought she was playing so well again and I hope she gets better and keeps up her good play."