TENNIS fans at the US Open yesterday were more interested in seeing Melanie Oudin play than Roger Federer. Arthur Ashe Stadium was packed for the 17-year-old blonde from Marietta, Ga. — with Nicole Kidman and Keith Urban (above), golf legend Nick Faldo, and Olympic skier Bode Miller among thoseon hand — “but it kind of emptied out for the Federer match,” a spy reports.