Pavel Pardo's first-half free kick was enough to ensure that 10-man Chicago Fire overcame Vancouver Whitecaps at Toyota Park.
The experienced Mexico international midfielder fired into the top corner from 20 yards after 10 minutes, punishing Jun Davidson for a needless foul on Patrick Nyarko.
Chicago could have extended their advantage before half time but Dominic Oduro was denied by Joe Cannon when clean through.
Arne Friedrich was sent off with 21 minutes remaining after picking up two yellow cards within moments of each other - both for fouls on Darren Mattocks.
Vancouver were sparked into action by their numerical advantage and, with Barry Robson pulling the strings, they began to cause their opponents problems for the first time in the match.
However, they were unable to find an equaliser as Robson and Camilo Sanvezzo fired narrowly wide from just outside the area and Eric Hassli's close-range header was well saved by Sean Johnson.
