Alfred Riedl's side won all their games en route to the final and were heavy favourites heading into the final over two legs.
But the Garuda now face an uphill task after being shocked 3-0 by the Malaysia in Kuala Lumpur during the first leg.
The Indonesians will take encouragement from their 5-1 defeat of their final opponents in the opening group fixture.
Speaking ahead of the second-leg in Jakarta, team manager Andi Darussalam revealed the spirit remains positive in the camp despite the mammoth task at hand.
"We know our position is not good because we are trailing by three goals and we will have to attack right from the start of the game," said Darussalam to affsuzukicup.com on Tuesday.
"But at the same time, we must also be careful in defence because we showed some weaknesses there in our last game and coach Riedl has been doing some work with our defenders to improve things in that area.
"We had conceded only two goals in the previous five games so I don't know what happened to our defence during the first leg. For their first goal, the ball should have been helped out of play by our defender (Maman Abdurachman). But suddenly, he was put under pressure by their forward (Norshahrul Idlan) and they managed to score.
"That's where the problems started for us because Malaysia then scored two quick goals after that which upset our players."
Indonesia will be hoping for help from their 12th men - the fans, who boosted the players' confidence after giving them a strong reception at their return from KL on Monday.
"We began training soon after we got back from KL and we are all working to try to build up the confidence of the players again for the second leg.
"They are now in good shape as we had a training session and the fans that were there were fantastic because they give a lot of encouragement to the players. The players do not want to let them down and we hope that they give good support to our team on Wednesday."
History will be made on Wednesday as either side will lift their first ever ASEAN title.