tennis 4 hours ago Modern tennis legend Rafael Nadal officially retires One of the world’s greatest tennis players, Rafael Nadal, officially retires following loss in the Davis Cup. US & World Videos 2:08 What color are tennis balls? 1:09 What is a ‘Golden Slam' in tennis? 0:46 Djokovic finally gets his Olympic gold medal 1:43 Team USA's Austin Krajicek secures silver in men's double tennis 2:57 US tennis stars on winning silver medals at men's doubles: ‘Experiences we'll never forget'
