The Bavarians, who lead Group A with 10 points, three ahead of Manchester City, are all but assured a spot in the knockout stage with Napoli third on five points.
They can also tie up first place if they win and City fail to beat Napoli.
"We were not aggressive enough and our movement at the back was not good," Heynckes said.
"I am certain my team will present itself differently on Tuesday," Heynckes said after the 1-0 loss to Dortmund. "One player or another seemed to be lacking the necessary tension and concentration against Dortmund. That will change."
Club CEO Karl-Heinz Rummenigge said the "painful" defeat to Dortmund should be put behind them fast.
"Now there is only victory for us on Tuesday. Then we can book our spot in the round of 16 and that is our duty," Rummenigge told reporters.
Juan Carlos Garrido's side, missing injured first-choice strikers Giuseppe Rossi and Nilmar, claimed only their third La Liga victory of the campaign on Saturday, a 1-0 home win over struggling Real Betis that put them on 14 points from 12 matches.
"You cannot be on top every year but we will always try," central defender Rodriguez told reporters. "Up to now we have known how to pick ourselves up from the reverses we have suffered, which to be honest have been a lot," he added.
"Now we have to focus on the Munich game and cling to the hope of continuing in the Europa League, although the truth is that it won't be easy and we'll have to work very hard."
