Unrein made four starts at defensive end last season and played in 14 games. He signed with the Bears after playing two games and then being waived by the Chargers.
Unrein, 28, is a former undrafted free agent who played for the Broncos from 2011-14. He signed a two-year deal.
Mariani, 28, signed a one-year deal. He’s spent the last two seasons returning kicks and playing as a backup wide receiver for the Bears, though he started five games last year and set new career highs with 22 catches for 300 yards.