A 2010 Pro Bowler with the Kansas City Chiefs, Cassel has reached a stage in his career where he's better off holding a clipboard. His teams are 8-19 over his spot starts in the last six seasons, dating back to his final year with the Chiefs. The Lions will be Cassel's fifth team since 2013.
While Stafford struggled to stay healthy early in his career, the Lions have not had much of a need for a backup in recent years. He has played in all 16 games each of the last seven seasons. Jake Rudock, the Lions' backup last year, attempted all of five passes.
No Lions backup has attempted more than 40 passes since 2010.
Cassel has thrown for 17,449 yards and 104 touchdowns against 81 interceptions during his NFL career.