The Crusaders, without at least seven front-line players through injury or suspension, controlled the ball through their forwards, punished their opponent's poor discipline and produced a bruising defence to drive them back behind the advantage line.
Lock Scott Barrett, prop Michael Alaalatoa and loose forward Heiden Bedwell-Curtis crossed for the home side, while Reed Prinsep scored a late consolation try for the visitors.
The Crusaders held a narrow 7-6 lead at halftime, but dominated the second spell to set up their ninth successive win of the season.