George Best at 18, during his first season for United, 1964.
Fabio Capello, probably 1967.
18-year-old Zinedine Zidane v Scotland in the 1991 Toulon Tournament. France reached the final where they lost 1-0 to England, thanks to a late goal by tournament MVP Alan Shearer.
Michel Platini in 1976, a day before he turned 21.