Monterrey played without injured forward Humberto Suazo, who has one career goal in the competition, but that did not stop it from taking a ninth minute lead. Jesus Corona - Suazo's replacement - started and finished a well-worked sequence that saw the 19-year-old score from three-yards out off after the reliable Aldo De Nigris provided a telling pass from the left.
De Nigris could have doubled the lead shortly afterwards, but his close-range header was easily clasped by Ulsan goalkeeper Kim Youngkwang.
Despite dictating the game, the Mexican side did not net its second until a brilliant back-heel by Corona found De Nigris, who one-timed a short pass to a mobile Delgado. The Argentine only had to touch it into an open net for the 77th minute tally.
Delgado completed his brace seven minutes later, taking a pass from Walter Ayovi on the edge of the box, feigning a defender and rifling home with his right foot.
A speculative 35-yard effort from Lee Keunho with two minutes remaining eluded Monterrey goalkeeper Jonathan Orozco, who will have been disappointed not to have made the save.
In last year's quarterfinal stage, Monterrey fell to Japan's Kashiwa Reysol 4-3 on penalty kicks after a 1-1 draw. The victory over Ulsan Hyundai, and the style in which it was achieved, will certainly boost the confidence of the two-time reigning CONCACAF champion heading into Thursday's showdown against Chelsea.