Mitchell reverted to the Lions' practice squad Monday, per the NFL's transaction log.
The Lions signed Mitchell to their practice squad Wednesday.
Mitchell (hand) was placed on injured reserve Saturday.
Mitchell (hand) has been ruled out for Sunday's wild-card round game against the Rams, Eric Woodyard of ESPN.com reports.
Mitchell (hand) was a limited participant at practice Thursday.
Mitchell caught one pass for four yards during Saturday's 20-19 loss to the Cowboys.
Mitchell played six of the Lions' 66 snaps on offense and went without a target in Saturday's 42-17 win over the Broncos.
Mitchell (hamstring) is active for Sunday's matchup against the Ravens.
Mitchell (hamstring) did not participate at practice Thursday.
Mitchell (hamstring) is inactive for Sunday's contest against the Panthers.