Knapp agreed to a contract with the Pirates on Tuesday, Jason Mackey of the Pittsburgh Post-Gazette reports.
The Pirates haven't disclosed the terms of Knapp's contract, but after he was granted his release from Cincinnati earlier Tuesday, he's presumably joining Pittsburgh on a one-year, major-league deal to serve as the backup to No. 1 catcher Roberto Perez. Knapp was unable to beat out Aramis Garcia for the backup catcher job with the Reds, but the 30-year-old likely won't face much competition for the No. 2 spot in Pittsburgh. Knapp and Perez are currently the only catchers on the Pirates' 40-man roster, and top prospect Henry Davis is at least a year away from reaching the majors.