Allen, a fourth-round pick in 2011, finished his career in Pittsburgh with 150 tackles, 34 passes defended and six interceptions. He missed 15 games with a knee injury last year and was benched in 2014 after struggling with injuries and poor play.
ESPN reported in March that the Steelers asked Allen to take a pay cut from his due salary of $4.4 million. Allen wasn't open to such a cut, so the team was prepared to move on.
Coach Mike Tomlin said last month that he wasn't certain Allen would be a factor in the team's cornerback lineup, citing the uncertainty around Allen's health. Allen dealt with a knee cartilage issue during the past season and spent much of the year on injured reserve.