The 62-year-old expects an evenly balanced encounter when two of his former teams lock horns at the Santiago Bernabeu
Bayern lost their unbeaten status in Bundesliga following defeats against Augsburg and Borussia Dortmund, while Madrid were beaten by Barcelona and Sevilla in La Liga.
Nevertheless, Breitner has little doubt that both sides will be back to their usual best when they lock horns at the Santiago Bernabeu on Wednesday.
"There have been a few parallels between the two clubs over the past two or three weeks. Real, like Bayern, have taken a breather," Breitner told Bayern's official website.
"They could have conceded four, five or six goals at Dortmund and then they would have been knocked out.
"Real Madrid and Bayern both know when they have to concentrate fully and when they can ease off a bit. I think there’s great mutual respect between the teams.
"But I hear the same things in Madrid and Munich: 'We'll go through.' Every side thinks the other is a bit weaker.
"All matches between Real and Bayern are passionate, so it’ll be another exciting encounter on Wednesday. That's all part of it."
Bayern and Madrid last met in the semi-finals of the Champions League in 2011-12, when the Bundesliga champions eventually emerged victorious after penalties.