The move clears $4.55 million in salary.
Marshall signed a three-year, $16 million contract last season, but only played four games due to a back injury. He was paid $6 million for those four games.
Marshall was in competition for a starting cornerback job with Jimmy Wilson.
Marshall, 28, played his first five seasons with the Carolina Panthers after being drafted in the second round of the 2006 NFL Draft. He has 18 career interceptions in 100 games played.