A-League champions Sydney FC will have to climb the tallest mountain if they want to be crowned kings of Asia this season.
The Sky Blues were grouped with two-time champions Jeonbuk Motors in Group H alongside former winners Gamba Osaka from Japan and Singapore's Tampines Rovers, in Wednesday's draw.
It is a group of death with the top two progressing, along with the three best finishing third-placed teams from all the groups, giving Sky Blues coach Steve Corica plenty to think about.
Brisbane Roar, who will playoff with Kaya-Iloilo of the Philippines and Chinese Super League side Beijing Guoan, also face a tough test should they advance to the group stage.
They will come face to face with defending champions South Korea's Ulsan Hyundai, who beat Iran's Persepolis in the final of last year's competition to win the title for the second time.
Thailand's BG Pathum United and fellow newcomers Viettel from Vietnam in Group F also await.
Forty teams will participate in the group phase of the competition - an increase from 32 last year - with the winners of each group plus the three best runners-up from the west and east regions advancing to the last 16.
Two-time champions Guangzhou FC - formerly known as Guangzhou Evergrande - take on Japanese champions Kawasaki Frontale in Group I as well as tournament newcomers United City from the Philippines.
The group will be completed by the winners of the playoff between South Korea's Daegu FC and Chiangrai United from Thailand.
In the western half of the draw, Saudi Arabia's Al Hilal, who won the title in 2019, will meet Shabab Al Ahli from the United Arab Emirates as well as debutants FC Istiklol from Tajikistan and either Qatar's Al Gharafah or AGMK from Uzbekistan.
Persepolis, who have been runners-up twice in the last three seasons, headline Group E, where they will meet Qatar's Al Rayyan, FC Goa from India and the winners of the playoff between Al Wahda from the UAE and Iraq's Al Zawraa.
The group phase of the competition is due to be played on a centralised basis due to the ongoing COVID-19 pandemic, with member associations asked by the Asian Football Confederation to submit bids to host the competitions in their respective regions.
Matches are scheduled to begin in April, with the knockout rounds slated to be played from mid-September. The final will be held over two legs on November 21 and November 27.
2021 AFC Champions League draw
Group A: Al Hilal (Saudi Arabia), Shabab Al Ahli (UAE), FC Istiklol (Tajikistan), Playoff Winner
Group B: Sharjah (UAE), Tractor FC (Iran), Pakhtakor (Uzbekistan), Playoff Winner
Group C: Al Duhail (Qatar), Al Ahli (Saudi Arabia), Esteghlal (Iran), Al Shorta (Iraq)
Group D: Al Sadd (Qatar), Al Nassr (Saudi Arabia), Al Wehdat (Jordan), Playoff Winner
Group E: Persepolis (Iran), Al Rayyan (Qatar), FC Goa (India), Playoff Winner
Group F: BG Pathum United (Thailand), Ulsan Hyundai (South Korea), Viettel (Vietnam), Playoff Winner
Group G: Jiangsu FC (China), Nagoya Grampus (Japan), Johor Darul Ta'zim (Malaysia), Playoff Winner
Group H: Jeonbuk Motors (South Korea), Gamba Osaka (Japan), Tampines Rovers (Singapore), Sydney FC (Australia)
Group I: Kawasaki Frontale (Japan), Guangzhou FC (China), United City (Philippines), Playoff Winner
Group J: Shandong Luneng (China), Port FC (Thailand), Kitchee (Hong Kong), Playoff Winner.