The first, and fundamental, question that we have to ask ourselves as goalkeeper coaches who are preparing the players we work with for the game in this theme could be:'How does a different goal size change the way that the goalkeepers save the ball, and the most common actions that they undertake?'
For coaches who already have experience working in a number of different formats within the game, such as futsal, the foundation phase's 7-a-side goals or disability formats, you will already be accustomed to the different strategies that goalkeepers use (i.e shot stopping techniques) to keep the ball out of the goal.
Of course, in the mainstream format we are always trying to develop the goalkeeper to be best equipped for the 11-a-side game, but younger goalkeepers often find novel and innovative styles for the smaller goal size that they are working with in any particular moment.
Beyond this, perhaps we can start to think about, in the senior game, the different behaviours required for the goalkeeper if the size of the goal changes, and therefore the characteristics and competencies that our goalkeepers need to have.
First, though, we have to understand the idea of affordances and constraints in relation to the game, and how changing the conditions (goal size) that we play under may drive different responses (actions) for the goalkeeper.