A "system of play" in soccer is a way to organize the players on the field so that each player has a specific responsibility within the system. On full-sized fields with 11 players on a team, a system of play always has "attackers", "defenders" and "midfielders" (linking the previous two) in addition to the ubiquitous goalkeeper. The variations come in deciding how many players to assign to each role and the exact "shape" the formation will take. Coaches sometimes get too obsessed with the relative merits of one system of play or another. The truth is that players win games, not systems of play, although they can definitely help. It's also the case that the system you pick should suit your particular group of players - it's hard to play a particular system if you don't have the right mix of players. Finally, the strengths of your opponents may cause you to alter your chosen of system of play.
In youth soccer, coaches have to be mindful of another aspect. Are the players capable, mentally and physically, of understanding and carrying out the system? Since the advent of small-sided games, which were partly motivated by the need to simplify the systems of play for very young players, coaches also have to adapt the traditional 11v11 systems to smaller player numbers. For background on that subject see the article " Playing Position versus Team Shape ".
In this article, we will discuss systems of play for different player numbers and age groups within the Palo Alto AYSO program, and make some recommendations. We want to stress right away that it is all too easy for a coach to sacrifice overall player development in the pursuit of a system of play. The main focus of youth soccer must be player development and for very young players (below 11) this means that skill development and active participation in the game are far more important than learning to play a position.
Systems of play are identified by two or three numbers, for example, 3-3 or 3-3-2. The goalkeeper is never included and the numbers start with the number of defenders, and finish with the number of attackers. A midfield is indicated by there being 3 numbers, otherwise the midfield is absent (for 7v7 and smaller). In any system of play, all players have both defensive and attacking responsibilities. Typically the breakdown would be as follows:
Position Time attacking Time defending
Attacker 75% 25%
Midfielder 50% 50%
Defender 25% 75%