Belgium's Kim Clijsters will be out of action for at least four weeks after tearing a hip muscle, her agent said in a statement on Wednesday.
"Kim has got an excess of fluid in her right hip joint, which turned out to be a deep muscle tear in her hip," the statement said.
The former world number one was beaten by her compatriot Yanina Wickmayer in the last 16 of the WTA tournament in Miami, Florida, and had complained of pain in her right hip at the end of the warm-up.
"The pain got worse during the match, making it more difficult for her to move," the statement added.
Clijsters expects to return to competition in the clay court tournament in Madrid, which starts on May 4.
The latest set-back led the Belgian press to speculate on whether Clijsters would retire but the 28-year-old on Tuesday "vigorously denied" wanting to end her career.