Bentley, 26, is a former third-round pick of the Lions back in 2012. He had one year remaining on his four-year, $2.649 million rookie contract, which included a base salary of $660,000 for the 2015 season.
According to OverTheCap.com, releasing Bentley will free up $680,000 in available cap space while creating $137,278 in dead money.
In 2014, Bentley was limited to appearing just two games after he sustained a season-ending ACL injury in earlier September.
During the 2013 season, Bentley appeared in 13 games for the Lions and recorded 29 tackles and five pass defenses. Pro Football Focus had him rated as the No. 82 cornerback out of 110 qualifying players that year.