Sepahan, the 2007 continental runners-up, and Nagoya have received only one caution each.
Sepahan have won all their three matches to top Group A with nine points while Nagoya are languishing at the bottom of Group F with one point from two games.
They will play their third match on April 12 against UAE’s Al Ain.
Korea Republic’s Jeju United, Al Ain and Japan’s Kashima Antlers are following the leaders with two cautions each while three players each from Melbourne Victory (Australia), FC Seoul (Korea Republic), Hangzhou Greentown (China) and Sydney FC (Australia) picked up yellow cards.
Saudi Arabia’s Al Nassr have the most yellow cards with their tally reaching 13 apart from one red card. Chinese side Shandong Luneng have 12 yellow and one red card.