The margin for error is tight as only the winners of the seven groups progress to the quarterfinals, where they will be joined by defending champions Urawa Reds of Japan.
Chunnam, bottom of its domestic K-League, is in last place in Group G and host surprise leader Chonburi of Thailand.
"We haven’t given up yet as we can still progress to the next round," Chunnam coach Park Hang-seo said.
Most eyes however will be on Australia where Melbourne Victory host Japanese club Gamba Osaka.
Melbourne is looking to bounce back from a 3-1 defeat in Thailand in the last round, while Gamba sits in third place in the J-League and showed its goalscoring capability in a roller-coaster 4-3 win at Chunnam last month.
"Obviously it is a long trip and will be a tough environment to play in, but we will go to Australia looking for a win," said Gamba’s prolific Brazilian striker Bare. "I’ll do what I have to do to help the team bring home three points."
Japanese champions Kashima Antlers lead Group F and are in fine form after a 9-1 victory over Krung Thai Bank and a 6-0 thrashing of Nam Dinh of Vietnam, as well as leading the J-League after winning their last 15 domestic matches.
Wednesday with be a different matter as Beijing Guoan of China, also with six points from the opening two games, provide the next opposition.
"It will be difficult but we have a good chance being at home in the first game," Kashima coach Oswaldo Oliviera. "We have to do our best to win this game and put ourselves in a comfortable position. I think whichever team wins this game will go on to win the group."
In Group E, Australia’s Adelaide United lies in second place behind leaders Changchun Yatai of China and travels to Vietnam to take on last-placed Binh Duong.
Adelaide coach Aurelio Vidmar is guarding against complacency.
"I don’t think we’re over confident but there is a danger of thinking that we’re going to go there and the game is going to be done and dusted before we even get onto the park," Vidmar said.
Chinese champion Changchun hosts Korean counterparts Pohang Steelers, which is in a form slump and faces elimination from the Champions League if defeated.
"It’s going to be a tough game for us," said Pohang’s Brazilian boss Sergio Farias as his team departed for northeast China. "Changchun will come at us strongly from the start, but as time passes I expect us to take control of the game."
In West Asia, Sepahan, which leads the Iranian league, must defeat 2004 and 2005 champions and Group A leaders Al-Ittihad of Saudi Arabia. Al-Ittihad of Syria and Uzbek club Kuruvchi both have three points and meet in the northern Syrian city of Aleppo.
In Group B, the top two teams meet as Iran’s Saipa, still coached by national team boss Ali Daei, travel to the temporary Kuwaiti home ground Iraqi club Al Quwa Al Jawiya. UAE titleholders Al-Wasl are yet to earn a point, but can move into third place with a home win against Kuwait SC.
The situation is similar in Group C with Qatar’s Al-Sadd in second place and hosting 2006 runners-up and group leaders Al-Karama of Syria. At the bottom, whichever team loses between Saudi Arabia’s Al-Ahli, who fired Serbian coach Nebojsa Vuckovic on Monday, and last year’s semifinalists Al-Wahda of UAE will be facing early elimination.
Group D is more open with leaders Al-Qadsia the only team to have won a game. The Kuwait league runners-up host newly crowned Qatar champions Al-Gharafa. Uzbekistan powerhouse Pakhtakor has a solitary point and needs a win at home to Arbil of Iraq.