 And 14-year-old Philadelphia Union midfielder Kaven Sullivan became the youngest player in Major League Soccer history Wednesday night and probably the youngest to play in any of the biggest professional sports leagues in the world. Sullivan was 14 years and 293 days old when he entered Philadelphia's home game as a substitute in the 85th minute against the New England Revolution. That makes him about two weeks younger than Freddie Adu when he made his MLS debut.