The Mutua Madrid Open announced that flu has forced top seed and two-time champion Serena Williams to withdraw from this year's tournament.
WTA Staff

MADRID, Spain - World No.1 and former champion Serena Williams has withdrawn from this year's Mutua Madrid Open.

The tournament announced on Friday morning that Williams was suffering from flu, ruling her out from returning to the tournament she won in 2012 and 2013.

"Unfortunately, I have to withdraw from Madrid because I've been battling the flu and I'm not at 100%. I look forward to returning soon," Williams said.

In her absence, Agnieszka Radwanska has been elevated to No.1 seed and at Friday's draw was paired with former French Open semifinalist Dominika Cibulkova.

Williams, who is the defending French Open champion, is now scheduled to open her clay court campaign at the Internazionali BNL d'Italia in May.