Cavan Sullivan became the youngest player in Major League Soccer history at 14 years 293 days when came on as a late substitute for Philadelphia Union on Wednesday night. The midfielder entered the pitch in the 85th minute of the home game against New England Revolution, a minute after his 20-year-old brother, Quinn Sullivan, had scored the final goal in their 5-1 win. Sullivan is 13 days younger than previous record holder Freddy Adu, who made his debut for DC United in 2004 at 14 years 306 days. It is a record for America team sports overall, and also below that from the major European footb…