Gamba Osaka and Pohang Steelers will be formidable opposition for Adelaide.
How they got here: Finished third in 2010-11 A-League. Won qualifying play-off against 2010-11 Indonesia Super League champions Persipura Jayapura. ACL history: Fourth appearance. Best finish: The giant-killing Reds of 2008 became the first Australian team to make the final of the AFC Champions League, but were outclassed 5-0 on aggregate in the two legs of the decider against Gamba Osaka.
Key players: Sergio van Dijk - Undoubtedly Adelaide's go-to striker, van Dijk is trying to rush through the necessary paperwork so that he can represent Indonesia. This ACL campaign will be an opportunity for him to adjust to a higher level of football, which is what he'll face at international level.
Dario Vidosic - Reds hero Marcos Flores is long gone, but sometime Socceroo Vidosic has done well to fill in as chief playmaker in his absence. How much longer he'll remain at Adelaide is another question, but there's no doubt he stands as the club's preferred creative outlet.
How they got here: Finished third in 2011 J. League. ACL history: Sixth appearance. Best finish: Gamba took out the 2008 Champions League in style, with a famous comeback win over Japanese rivals Urawa Red Diamonds in the two legs of the semi-final. They drew the first match 1-1 and then were down 1-0 at half time in the second, but scored three late goals to confirm their place in the final.
Key players: Yasuhito Endo - Still one of the classiest players in Asian football, Australian fans will remember Endo as the architect of Adelaide's downfall four years ago - and as a member of the Japan side that beat the Socceroos in the final of last year's Asian Cup.
Takahiro Futagawa - A little further ahead of Endo in midfield is Futugawa, who pulls the strings in attack for Gamba. Another experienced head with an eye for goal and a great passing range, he'll be a central figure during the Japanese club's run at more Asian glory.
How they got here: 2011 Uzbek League champions. ACL history: Fifth appearance. Best finish: Brazilian legend Zico was at the helm in 2008 when 'the Swallows' made the semi-final of the ACL, but their fate was sealed when Adelaide put three goals past them at Hindmarsh Stadium in the first leg. They haven't made it past the quarter-finals since.
Key players: David Carney - Something of a surprise addition to Bunyodkor's squad, we all know what Carney is capable of on his day. One imagines the Socceroo stalwart will play a little further up the park at his new club, which will allow him to bring the best out of his trusty left foot.
Anvarjon Soliev - A member of the Uzbekistan national team, gun striker Soliev has been there and done that when it comes to the ACL. Having made a total of three semi-final appearances with Bunyodkor and former club Pakhator Tashkent, the veteran marksman knows how to score and has no problems doing so wherever the ACL may take him.
How they got here: Finished third in 2011 K-League. Won qualifying play-off against 2011 Thai Premier League runners-up Chonburi. ACL history: Fourth appearance. Best finish: The Steelers won the Asian Champions League in 2009, when they were drawn in the same group as Central Coast. After finishing top of their pool, they eventually met Saudi club Al-Ittihad in the final and were 2-1 victors.
Key players: Derek Asamoah - The former Northampton, Lincoln City and Shrewsbury forward is a proven goal threat, capable of playing almost anywhere in the final third. With excellent skills and pace to burn, the Ghanaian had a good first season with Pohang in 2011 and will play a major part in their ACL campaign this time around.
Ianis Zicu - A new addition to Pohang's squad, Romanian international Zicu comes to South Korea with a good pedigree. Last season, the attacking midfielder was brilliant for Bulgarian club CSKA Sofia, finding the net 13 times before transferring to the Steelers.
Who will make it through: Consider this the group of nostalgia for Reds fans. Adelaide United have faced all three of these teams before - and all in 2008, when their magical Champions League run captured the fascination of football fans across Australia. But their recent form suggests they won't be able to replicate those feats in their surprise fourth appearance in Asia's premier club competition. There's two clear candidates for progression, and both are Asian powerhouses and previous winners of the tournament - Gamba Osaka and Pohang Steelers. They will be formidable opposition for Adelaide and Bunyodkor - the former is now a vastly different team to the one that won qualification by finishing third last season, and the prospect of three globetrotting trips from Uzbekistan may be too much to muster for the latter.