Small-sided games (SSGs) are popular because they train fitness, technique and decision-making at once. But they are not a perfect replacement for every type of conditioning.
Smaller pitches and fewer players tend to raise heart rate and the number of accelerations, decelerations and duels
Larger pitches allow more high-speed running and sprinting, which small games often lack
Rules change the load: touch limits, number of players, coach encouragement and bout duration all matter
Load varies widely between players in the same game, so not everyone gets the same stimulus