Effects of free-play or introducing artificial rules on tactical behavior based on soccer-team lines: A pilot study.

This study focused on assessing the effects of playing modified soccer games freely versus under artificial rules on tactical behavior based on team lines during the team-possession phase in two Spanish youth categories: under-14s (U-14s) and under-16s (U-16s). Thirty-two players from a LaLiga-affiliated club were divided into free-play and conditioned groups and participated in four training sessions involving eight-on-eight games using a 1-3-3-1 formation. Tactical behavior was analyzed through positional data using geometrical primitives—centroid position changes, interpersonal distances (dyads), and surface area—and their approximate entropy to measure behavioral regularity. Results indicated that short-term free-play training notably enhanced tactical regularity and spatial organization in U-14s team lines, especially in the goalkeeper-defender subgroup, while U-16s showed minimal changes. The findings suggest that free-play may strengthen meso-level tactical patterns in younger youth players, though limitations such as sample size and game format restrict generalization.