At 36, Andre Agassi thrilled tennis fans last night with a comeback victory over a 21-year old opponent. But whether he wins or loses his next match, Agassi has declared that his career will end when this year's US Open is over. As one of a long line of athletes who've kept America at the top of the tennis world heads into the sunset, is there anyone to replace him? Does America have a bright future in the world of professional tennis?