The Lions released quarterback Jake Rudock on Saturday, according to multiple media outlets, leaving journeyman Cassel as the backup to starter Matthew Stafford.
Detroit also cleared out its cluttered backfield in trimming its roster to the league-mandated 53 players, placing running back Zach Zenner on injured reserve and waiving running back Dwayne Washington.
Rudock served as the backup for the Lions in 2017. He appeared in three games and attempted five passes, completing three for 24 yards and an interception. He was a sixth-round pick in the 2016 NFL Draft out of Michigan.
Cassel is with his seventh NFL team since he was taken by the New England Patriots in the seventh round in 2005.
The 36-year-old Cassel has appeared in 106 career games, including 81 starts, with the Patriots, Kansas City Chiefs, Minnesota Vikings, Buffalo Bills, Dallas Cowboys and Tennessee Titans.
He started 15 games in three consecutive seasons with the Patriots and Chiefs from 2008-10, but appeared in only six games over the past two seasons with Tennessee, making two starts.
Cassel is 36-45 as a starter, throwing for 17,449 yards with 104 touchdowns versus 81 interceptions.
Zenner had only 14 carries for 26 yards and a touchdown last season after rushing for 334 yards and making four starts in 2016. An undrafted free agent out of South Dakota State, he suffered a back injury in Thursday’s preseason finale.
Washington also was a sparse contributor in 2017, rushing for 44 yards and 20 carries. A seventh-round pick in 2016, he carried 90 times for 265 yards and a touchdown as a rookie.
Detroit bolstered its backfield in the offseason by signing free agent LeGarrette Blount and drafting Auburn’s Kerryon Johnson in the second round.