Knapp was released by the Tigers on Tuesday, Jason Beck of MLB.com reports.
The veteran catcher had posted a .253/.337/.397 batting line through 70 games (267 plate appearances) this season with Triple-A Toledo. Knapp has had some wild swings in production during a big-league career that dates back to 2017, but given he's still just 31 years old, it's certainly conceivable he gets a fresh start with another organization.