To be a professional football player is not a short process, it is a long process. The process starts in childhood. Football is not like other sport which can keep the curve up until later of age. Many football players finish their careers in the 30th years of age, in contrast to arm-wrestling which best curve can achieve in the 30th years of age. Everybody can start to play football at age 5, the big focus should be on flexibility and coordination, then in the age of 8, the technique and tactics should be added to the training program, and in the age of 13 balance and strength training can be added to the training program.
Later in the 15 years of age speed can be added. In the adolescent age, mental coaching is very important. Youth need too much inspiration to produce more skills. So, all these skills which be learned from the age of 5 until the end of the carrier should be performed from time to time because everything if you don't use it, you lose it. Especially flexibility skills. An athlete can be a professional at the age of 18 if he or she follows this process.