9. Adnan Januzaj
Adnan Januzaj has his whole career ahead of him - and on the basis of his incredible debut season at Manchester United, there's no reason why the 19-year-old won't be worth an absolute fortune in a few years' time.
The Belgium-born winger is reportedly already valued at over £40m, according to recent reports, and should be worth double that in three of four years.
Could the Red Devils' prodigy even become football's first £100m player?