World number three Maria Sharapova and 10th-ranked Daniela Hantuchova have pulled out of next week's German Open in Berlin, organisers said on Wednesday.
Russian Sharapova, who won her third Grand Slam title when she lifted the Australian Open in January, said she did not feel fit enough to play.
"I'm working hard to get back on court as quickly as my body will allow," said Sharapova in a news release without being specific about her fitness problem.
Slovakian Hantuchova is recovering from a stress fracture in her right foot.
World number one Justine Henin, a triple champion in Berlin, and holder and second-ranked Ana Ivanovic are due to play in the $1.3 million event.
Another five top-10 players, including American Serena Williams, are also in the draw.