The world number one admitted she is "worried" by an ongoing back problem that places her participation at the WTA Finals in jeopardy.
Simona Halep was forced to retire in the first round of the China Open after suffering a reoccurrence of her troubling back injury.
The world number one dropped the opening set 6-1 against Tunisian qualifier Ons Jabeur before declaring she was unable to continue.
Halep, who has already qualified for next month's WTA Finals, battled the same issue during a lacklustre 6-0 7-5 defeat to Dominika Cibulkova at the Wuhan Open last week.
Her latest setback continues a difficult couple of months, the 27-year-old having been stunned by Kaia Kanepi in the first round of the US Open after claiming her maiden Grand Slam title at the French Open in June.
"I'm just worried now. I feel sad that I couldn't finish," Halep said after the match.
"I don't know exactly what it is. I will go home. I will have an MRI and I will see."