In the modern game, teams spot players at ever younger ages. They are put through development programs that are designed to squeeze every ounce of ability out of them. It is no wonder that some players burn out and fail to make the cut.
These young players are often highly exciting with huge amounts of natural ability. Every season, there are dozens of these young players making headlines as clubs pay truly gargantuan sums of money for teenagers with little top-level experience.
Many of them turn out to not have what it takes to survive at football's top table, but some do.
So, here is a list of the 10 best players under the age of 21 (that's under, not including) today.