Tennis-Reaction to Serena Williams announcing her retirement

FILE PHOTO: Serena Williams of the U.S. celebrates her victory against Maria Sharapova of Russia at the end of their women's singles final match at the Madrid Open tennis tournament in Madrid May 12, 2013. World number one and top seed Williams racked up the 50th title of her 18-year career when she thumped Sharapova 6-1 6-4 to defend her Madrid Open crown on Sunday. REUTERS/Juan Medina/File Photo

(Reuters) - Following are reactions to Serena Williams announcing on Tuesday that she plans to retire from the sport following the U.S. Open:

FORMER WORLD NUMBER ONE BILLIE JEAN KING