Serena Williams has pulled out of the Nasdaq-100 Open in Miami, which begins next week.
Serena Williams was last seen at the Oscars on 5 March
Williams, whose ranking has plummeted to a seven-year low of 58, cited a knee injury and lack of training.
"I am very disappointed but I need more time before I am able to compete at the highest level," said the 24-year-old.
Williams has not played since the Australian Open in January and has been fined by the WTA for pulling out of several tournaments this year.
She underwent knee surgery in 2003 and has not won a title since taking her seventh Grand Slam crown at the 2005 Australian Open.
She has only played in nine tournaments since.