An early goal by Jesus Corona and a second-half double courtesy of Cesar Delgado sent the CONCACAF champions through to the CWC semifinal against the European champion.
The Mexican outfit earned a prestigious clash with European champion Chelsea with a dominant display over the Koreans, who never looked like they were going to match their opponents. The game immediately started on a high just nine minutes after kickoff. Mexico international Aldo De Nigris crossed from the left and found teammate Jesus Corona in the penalty area, with Corona easily tapping home from close range after taking advantage of poor positioning from Ulsan's defense.
Los Rayados almost doubled their lead three minutes later, when an unmarked De Nigris headed directly into Kim Young-Kwang's hands from a favorable position. The Korean goalkeeper was then forced into a difficult save when he palmed away a drive from Cesar Delgado in the 17th minute, and the Mexicans continued to threaten their opponents' with a quick and energetic display.
In the second half, the Asian champions tried to come out from their shell early on with some aerial attempts, but it was Monterrey who again found the back of the net, only for the linesman to cancel out Sergio Perez's header for being offside.
Delgado opened his account on 77 minutes and got Monterrey its second goal after a classy combination with Corona and De Nigris and blew out Ulsan's hopes of coming back into the match. Delgado completed his brace seven minutes later, firing the ball past Kim after Walter Ayovi's pass from the right.
The Asian side found a late consolation through Lee Keun-Ho, with the Asian Footballer of the Year giving Korean supporters something to cheer about on a disappointing afternoon, with an effort from 25 yards that Monterrey goalkeeper Jonathan Orozco mishandled.
The K-League side is now set to face the loser of Sunday night's matchup between J-League champions Sanfrecce Hiroshima and African king Al-Ahly, while two-time defending CONCACAF Champions League winner Monterrey braces itself for a date with the Blues.