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, 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, while China's Jiangsu Sainty beat Buriram United to bounce from bottom to second in the same pool.
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.
China's Jiangsu had an easier evening in Nanjing after two goals in consecutive minutes put Thai visitors Buriram on the ropes just before half-time.
The hosts were already in the ascendancy when Le Bofei rifled in a rebound on 41 minutes, and they floored Buriram just a minute later when Sun Ke rose unmarked to head home Ji Xiang's cross from the left.
Sun had a second-half effort flagged off for offside as Jiangsu leapfrogged Buriram and Sendai to lie second in Group E, three points behind leaders FC Seoul.
Tuesday's action continues with Bunyodkor against Beijing Guoan, which is the competition's first game between teams from Uzbekistan and China, and four more fixtures in the Middle East.
The top two from each of eight groups will go into next month's round of 16 of the trans-continental competition, which then takes a mid-year break and does not wrap up until November.