Chivas USA forward Eduardo Lillingston, scorer of nine goals for his team this season, drilled a Cuauhtemoc Blanco corner kick into the wrong net midway through the second half and thus did the Fire win, 1-0, to wrap second place in the Eastern Conference.
The corner kick was the 14th of the game for Chicago, which was missing John Thorrington because of injury and left Justin Mapp on the bench, yet managed 13 shots in a game played under torrential rains. The Fire nearly took the lead on a corner in the 16th minute, but Chivas USA keeper Zach Thornton deflected a header by Brian McBride, and Gerson Mayen headed Brandon Prideaux's follow-up shot away from danger.
Thornton recorded his second and last official save later in the half when he turned away a long-distance drive from Chris Rolfe, who set up Baggo Hisidic for a chance a few minutes later that caromed off a defender and out for a corner.
On the own goal, Blanco swung his decisive corner kick three minutes after replacing Marco Pappa. Lillingston encountered no opposition as he met the ball but somehow it bounced off the side of his head and inside Thornton's near post.
Chivas USA, which despite losing can still win the Western Conference title, hosts Houston in its final game of the season Sunday. Chicago will play its first playoff game on the road next week at a location to be determined after finishing second to Supporters' Shield winner Columbus for the second straight season.
Oct. 22 in Bridgeview, Ill.
Chicago 1, Chivas USA 0. Goal: own goal (Lillingston) 67
Chicago -- Busch, Prideaux, Brown, Robinson, Banner, Nyarko, Husidic, Pause, Pappa (Blanco 64), McBride, Rolfe (Woolard 83),
Chivas USA -- Thornton, Bornstein, Cuesta, Thomas, Trujillo (Nagamura 46), Kljestan, Mayen (Santos 62), Saragosa, Padilla, Lillingston, Galindo (Braun 54).
Referee: Terry Vaughn.