Chicago took a shock lead in the 25th minute when Mike Magee latched on to Dilly Duka's through ball and slipped a shot past Michael Gspurning.
Seattle had a tremendous opportunity to get on level terms at the half-hour mark when Bakary Soumare was whistled for a hand ball in the box, but Sean Johnson denied Osvaldo Alonso's ensuing attempt from the spot.
The tying goal eventually came before the close of the first half as the Chicago defense failed to deal with a cross to the back post. Marc Burch collected possession for the Sounders and pumped it back in for Lamar Neagle to equalize from close range.
It looked as though the two sides would finish level at a goal apiece, but Seattle's late pressure saw the Chicago defense crack in the 89th minute. Zach Scott found space on the left flank and played a low cross to the top of the six-yard box. The delivery eluded a couple of Sounders players, but it made no difference for the home side as Segares turned the ball into his own net.
The result sees Seattle (14-8-4) extend its winning run to four games as the club improves to 46 points on the season, two points shy of first-place Real Salt Lake.
Chicago (10-11-5) drops its second straight road match to remain on 35 points.
09/08 00:21:58 ET