Frankfurt are currently fourth in the league standings with 37 points from 21 matches.
"I cannot recognise any sign which suggests they are going to suffer a collapse," Klopp told reporters.
"Frankfurt are playing an incredibly good season. The way they turn defence into attack is excellent, and they have Alex Meier who is having what seems to be the 47th second wind of his career.
"It is going to be a tough task for us."
Dortmund will head into Saturday's clash second in the table with 39 points from 21 matches.