Ivanovic beat Dinara Safina in the 2008 French Open final
Ana Ivanovic has withdrawn from the Madrid Open because of a knee injury but insisted she will be fit in time to defend her French Open title on 25 May.
The seventh-ranked Serb is struggling with an inflammation in her right knee and doctors ordered her not to play competitively for a week.
"It's become more painful with each match, so I decided to go and see a specialist in Munich," said Ivanovic.
The 21-year-old added there is "no danger" of her missing the French Open.
Ivanovic has been bothered by her knee problem since a Fed Cup match in April.
The former world number one had already suffered a setback ahead of the defence of her French Open title when she was beaten in the third round of the Italian Open by Poland's Agnieszka Radwanska.