Serena Williams is likely to be out for the rest of the year after she re-injured her right foot from over-training, she said on Sunday.
Williams had earlier pulled out of next week's Linz tournament in Austria.
However on Sunday she said the pain she felt on Saturday after training had meant she was now likely to be out for the rest of the year.
"I felt discomfort in my foot and tests by my doctor revealed that I had unfortunately re-strained it, as a result of over training (and) I am likely out for the year now," Williams said on her official website.
"I was really looking forward to beginning my comeback in Linz, followed by the year-end championships in Doha.
"I feel completely heartbroken, and devastated, but knowing I will never be given more than I can handle I plan on coming back stronger and better.
"However, in order not to make this worse, I have to chill on my physical workouts but I will immediately begin rehabbing as soon as I get the Doc's OK," she said.
The American, who has not played since she won her 13th Grand Slam at Wimbledon, had surgery after she cut her foot on broken glass at a restaurant in July.
The news completed a bad week for the younger Williams sister as her stint on the sidelines allowed Caroline Wozniacki to rack up enough ranking points to knock the 29-year-old off the top spot.
The Dane will be confirmed as the number one when the new WTA rankings are released on Monday.
