Former Asian title-holders Pohang Steelers dealt Sanfrecce Hiroshima's AFC Champions League bid a crippling blow Tuesday when they beat the Japanese team 1-0 away to leave them on zero points after three games.
Bae Chun-Suk's strike on 17 minutes condemned the J-League champions to stay rooted at the foot of Group G and needing a dramatic change in fortunes in their last three pool games if they are to reach next month's knock-out round of 16.
Elsewhere FC Seoul survived a late fight-back to beat Japanese visitors Vegalta Sendai 2-1 and extend their lead at the top of Group E. Pool rivals Jiangsu Sainty and Buriram United were contesting a later kick-off.
Sanfrecce badly needed a win to breathe life into their campaign but they were rocked by the early goal from striker Bae after a cross from Go Moo-Yul, who had breached the Japanese side's defence from the left.
Bae was denied a second by Hiroshima goalkeeper Shusaku Nishikawa's foot on 26 minutes, before Park Hyung-Jin came close to converting a chance at the other end.
South Korea's Pohang, the 2009 Asian champions, squandered several more goal attempts in the first half, while just before the break, Hiroshima midfielder Gakuto Notsuda headed Hironori Ishikawa's cross over the bar.
On the hour-mark, Naoki Ishihara was denied by the width of the post when he met Mihael Mikic's cross and headed off the woodwork.
Bae fired over shortly afterwards and Pohang again came close at the death when Cho Chan-Ho dribbled towards goal and fired off the right post.
"We have no choice but to win the last three matches and keep believing it's possible," said Hiroshima captain Hisato Sato. "We need to throw everything at the last three matches."
In Seoul, the hosts were cruising after first-half goals from Sergio Escudero and Kim Jin-Kyu, but they had to endure an anxious finish after Sendai's Brazilian forward Wilson reduced the deficit with an 87th-minute penalty.