Adelaide United lost playmaker Dario Vidosic to injury in their away defeat to Pohang Steelers in Tuesday night's Asian Champions League match in South Korea.
Pohang triumphed 1-0, with Vidosic limping off with a hamstring strain before a goalkeeping blunder by Adelaide captain Eugene Galekovic gifted the Steelers a score.
Galekovic fumbled a free kick in the 68th minute, somehow palming the ball between his legs and Steeler Kim Dae-Ho pounced and slotted a left footer from a tight angle.
Reds striker Bruce Djite's desperate defensive goal-line slide was officially debited an own goal as he made contact with the ball.
The Reds have two wins and the loss in their Asian campaign, with their marquee attacking weapon Vidosic straining a hamstring in the 33rd minute.
The Reds No.10 had been troubled by the hamstring leading into the fixture, which Pohang controlled offensively.
The Steelers dominated possession, and Ghana's Derek Asamoah was a constant threat, but Adelaide skipper Galekovic was forced to make just one save in the scoreless first half.
Adelaide held out until stung by a free kick from Wang Jin-Sung, whose testing left-footer curled towards near post.
Galekovic palmed the ball down in a regulation save, but lost control and over-ran the ball to give Dae-Ho the scoring shot.
Adelaide attempted to lift their tempo but were shut down by the Steelers, with two late free kicks from Cassio into the box their most meaningful moments.
Pohan joined Adelaide at the top of Group E with six points.
Adelaide's next two group games are at home, against Pohang on April 18 and Uzbekistan's Bunyodkor on May 2, before their last match, away against Japan's Gamba Osaka on May 16.