Bucharest - World No 1 Simona Halep, who retired during her first-round match in Beijing over the weekend, said on Tuesday she has a herniated disc.
"I had an MRI on my back and found out that I have a herniated disc," the 27-year-old Romanian wrote on social media. "I will consult doctors in the coming days and will keep you informed."
"I hope to be back quickly," she said, without offering any timescale.
On Sunday, Halep said she was "worried now" when a persistent back problem forced her out of the China Open after just 31 miserable minutes.
The Romanian never looked comfortable against Tunisian qualifier Ons Jabeur, losing the opening set of their first-round match 6-1 before calling it quits.
She said at the time she thought it was a different back problem from the one that contributed to her early loss in Wuhan a week earlier.
"I knew that there is pain, but I thought if I warm up during the match, it's going to be better, but it wasn't," she said.
The Romanian has been struggling with injuries over the later stages of the season. She dropped out of the New Haven tournament at the end of August with an Achilles problem and then lost in the first round of the US Open a week later.