With one matchday still to play, K-League leaders Pohang progressed to the next stage of the competition with a 2-0 Group E win at Japan's Cerezo Osaka.
Lee Myung-Ju scored the opener in the 24th minute and their triumph was sealed when Kim Seung-Dae converted Son Joon-Ho's assist midway through the second half.
Pohang are guaranteed to top the pool after their latest win.
The other three Group E sides are all locked on five points after Buriram United of the Thai Premier League edged Shandong Luneng 1-0.
Japan forward Kai Hirano scored the only goal 11 minutes before the break as the Chinese Super League outfit suffered defeat.
Saudi Arabia's Al Shabab will join Pohang in the round of 16 after Saeed Al Dosari's 95th-minute penalty gave them a thrilling 2-1 win over Esteghlal of Iran.
Also in Group A, United Arab Emirates outfit Al Jazira booked their progression with a 3-2 win at Al Rayyan in Qatar.
South Korean's Cho Yong-Hyung's own goal in stoppage time proved the difference.
Iran's Foolad came from behind to win 3-1 against El Jaish and seal their spot in the next stage.
The Group B encounter saw the Qatari side take the lead through Nilmar in the ninth minute.
Bakhtiar Rahmani and Gholamreza Rezaei scored before the break for the victors, though, before substitute Luciano Pereira Mendes wrapped up the win in the dying stages.
Uzbekistan's Bunyodkor beat Al Fateh of Saudi Arabia 3-2 in the other Group B clash. Goals in the last seven minutes from Vokhid Shodiev and Alibobo Rakhmatullaev sealed victory for Bunyodkor, who are third, three points behind the second-placed El Jaish.
And all four sides in Group F can still reach the last 16 after FC Seoul beat the Central Coast Mariners 1-0.
The K-League outfit needed some luck, though, with a John Hutchinson own goal in the 92nd minute condemning the Australian side to defeat in Gosford.
The other Group F match saw Sanfrecce Hiroshima come from two goals down to draw 2-2 at Beijing Guoan of China.
Naoki Ishihara bagged a second-half brace in the space of three minutes for the Japanese side.
Seoul have eight points from their five matches, with the three other sides all stuck on six.
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