At the intermediate level of play and above, tactical instruction begins to outweigh technical instruction. To aid in this instruction, player positions are replaced with a standard numbering system that provides:
- A consistent scheme/system across the United States, simplifying tactical discussions among disparate coaching staff
- Refinement of positions (e.g. a defensive vs center vs attacking midfielder)
- Shorthand for players and coaches to communicate (e.g. “use a 7-10-9 passing sequence” vs “winger passes to attacking midfielder, passes to forward”)
The concept of the numbering system has been in existence since the 20s and a specific US-based system was adopted in 2012. Here is the official publication from US Soccer.
This is appropriate for EXTRA teams beginning possibly at 10u but definitely at 12u. I do not recommend this for core teams below 14u.