It's the first time Monahan has been named a healthy scratch since April 3, 2019.
Monahan posted a career-high 82 points during the 2018-19 season, but his production has declined in succeeding seasons.
The 27-year-old has registered only 22 points (eight goals and 14 assists) through 63 games this year.
Monahan, who was selected sixth overall by the Flames in 2013, is signed through next season at a $6.375 million cap hit, according to CapFriendly.com.
The Flames (38-17-8) entered Friday's contest sitting first in the Pacific Division — with a five-point cushion on the second-place Los Angeles Kings — but have lost three of their past five games.