Kashiwa Reysol were forced into extra time in their 3-2 play-off victory over Thailand's Chonburi FC.
Their first group match sees them facing off against South Korea's Jeonbuk Hyundai Motors and coach Tatsuma says they will need to shift gears.
Tatsuma said: "It was our big goal to win the play-off and advance to the league, but we also prepared ourselves with the league matches on our mind. The first opponents haven't played an official match, so it's difficult to do scouting on them, but we want to keep the good mood from our play-off wins into the tournament.
"Of course we need to win every match in the group stage, but we have to play a little differently from in the play-off where it's 'win or go home'. We have to change our mind-set, but in the locker room after the Chonburi match, I think we have already done that."
Gamba Osaka coach Hasegawa Kenta has also thought about his strategy for the group stages, saying home games will be the key. Gamba Osaka's first match is against Group F opponents Guangzhou R&F at home.
Kenta said: "We want to win the title in Asia. The group stage is short and it will finish in early May. So the first priority is advancing out of it. To do that, winning at home and getting three points is most important.
"Countries in Asia have improved, but I think J.League clubs are good enough to advance. So the key is how well we can prepare for it to play up to the best ability of our players."