Bayern thrashed Barcelona 4-0 on Tuesday night in the Champions League semi-final but, despite such a handsome advantage, Heynckes will still rest several key players ahead of next week's return leg in Catalonia.
The Bundesliga title is already in the bag for Bayern but Heynckes' men will set a new points mark with a draw against Freiburg while a 20th clean sheet would create another league record.
It all amounts to a daunting prospect for fifth-placed Freiburg who have been the league's surprise package this season.
Christian Streich's men remain in contention for a place in the Champions League qualifiers - they are just a point behind Schalke in fourth - but know they must be perfectly prepared to take on Bayern.
"Of course we're looking forward to this game," said Streich. "It's certainly going to be interesting for us.
"We've just got to try to get it right tactically so that we don't make it so easy for Bayern.
"We've got to be compact and try to stick together, no matter where the ball is.
"We want to try to play our best game possible in Munich and then we will just have to see what we get out of it."
Streich will make changes to his side, although his alterations are enforced.
Julian Schuster is suspended while Jan Rosenthal is still not fit to return to the side. Daniel Caligiuri faces a late fitness test.
Bayern remain without long-term injury absentees Toni Kroos and Holger Badstuber.