Serena Williams of the United States celebrates after winning over Russia's Svetlana Kuznetsova during their Women's singles quarterfinal match at the Australian Open tennis championship in Melbourne, Australia, Wednesday, Jan. 28, 2009. (AP Photo/Rick Stevens)
MADRID (AP) - Serena Williams is out of the Madrid Open after aggravating a leg injury in a first-round match against Francesca Schiavone.
The second-ranked Williams retired after losing the first set 6-4 Monday.
She says her movement was hindered by a a recurring injury to her right leg.
Williams would not comment on the extent of the injury or whether it would keep her out of the upcoming French Open.