New Delhi: Serena Williams has withdrawn from the Madrid Open because of flu, the organisers said on Friday.
"Unfortunately, I have to withdraw from Madrid because I've been battling the flu and I'm not at 100 percent. I look forward to returning soon," Williams said in a statement.
Agnieszka Radwanska takes over as top seed for the tournament, which starts on Saturday, while Williams is now due to start her clay-court season in Rome.
The 34-year-old world number one has only played four tournaments since August, failing to win any of them.
She lost in the US Open semi-finals in September, before defeats this year in the Australian Open and Indian Wells finals and a round-four loss in Miami.