For every shot, there is an optimal goalkeeper position — a point within a "coverage cone" that maximizes the probability of saving shots across the range of possible trajectories from that shooting location. Tracking data enables computing this optimal position per shot and comparing it to where the goalkeeper actually was. Deviation from optimal is the primary positioning quality metric. Systematic deviation in a specific direction (hugging near post, standing too deep) reveals a correctable positioning habit.
Construction: for each shot, compute the optimal GK position from the cone defined by the shot location and goal dimensions; compare to the GK's actual tracked position; record the deviation vector. Aggregate over a full season to show: (1) average deviation magnitude; (2) directional bias (consistently too far left/right/deep); (3) worst-case outliers for clip review. Present to the goalkeeper coach with clip-linked outliers — "these are the 5 shots where positioning was furthest from optimal."
GK positioning biases (near-post hugging, standing too deep, consistent lateral offset) are detectable within 10-15 matches of tracking data but typically take coaching staff 2+ seasons to identify through video alone. The positioning deviation is sub-meter — invisible to the naked eye in real-time but clearly visible in aggregate tracking data plots. Once identified and shown to the GK with data, correction is fast (4-8 weeks of targeted training) because it's a positioning habit, not a physical limitation.