The Science of Goalkeeper Reflex: Sub-400ms Windows
At elite UEFA Champions League velocity (75–90 mph), a soccer ball travels from the edge of the 18-yard box to the goal line in roughly 400 to 520 milliseconds. From 6 yards out (e.g. Dimitar Berbatov's 90+4' point-blank header), that time collapses to just 240–300 milliseconds.
Human visual reaction time (optical recognition to motor cortex signal) consumes 160–200ms alone. This leaves a goalkeeper with barely 100 milliseconds to adjust their body shape, explode their center of mass, and position both 22-centimeter glove surfaces into the 7.32m × 2.44m (17.86 m²) goal mouth.
Understanding Post-Shot Expected Goals (PSxG)
Unlike standard Expected Goals (xG), which measures the quality of a chance prior to shot release based on shooter coordinates and defender pressure, Post-Shot Expected Goals (PSxG) assesses shot trajectory after the ball leaves the boot.
A strike landing exactly in the top 90 corner has a PSxG exceeding 0.85, whereas a central shot right at the keeper's chest carries a PSxG under 0.08. The difference between PSxG and actual goals conceded represents the true shot-stopping value added by a world-class shot-stopper like Casillas.