Blot, do not rub
Press a thick pad of white towelling firmly into the spot and stand on it. Weight and time do the work; the aim is to draw liquid upward into the towel before it travels further down. Replace the towel as it saturates and repeat until fresh towelling comes away nearly dry. Rubbing does the opposite of what you want: it drives liquid deeper into the backing and distorts the carpet pile, leaving a fuzzy patch that stays visible after the stain is gone.