Former Sydney FC star Brandon O'Neill was in the starting XI for Pohang Steelers as Seoul recovered from a woeful early defensive error to win 2-1 in K League 1.
Seoul were this week hit with a 100 million won (£66,000) fine after they mistakenly used sex dolls to fill spaces in their empty stadium during a 1-0 victory over Gwangju.
Matters on the field took a turn for the worse in the fifth minute of Friday's clash after a mix-up between Kim Nam-chun and goalkeeper Yu Sang-hun allowed Stanislav Iljutcenko to steal in and latch on to a backpass, gratefully tapping into an empty net.
Half an hour later Seoul were level as Hwang Hyun-soo glanced Park Chu-young's set-piece into the bottom-right corner.
Osmar struck the decisive blow in the 73rd minute, racing on to Ju Se-jong's corner at the near post to find the net with a powerful header.
The win moves Seoul on to six points, level with leaders Ulsan Hyundai and Jeonbuk Motors having played a game more.
Pohang have four points from their opening three matches.