Detroit coach Jim Schwartz said on Thursday that Bentley will have season-ending shoulder surgery. Bentley, a third-round pick, started in three of four games this season and made 13 tackles.
The Lions released Carey in August. He played in five games for Detroit last year and started in 10 of 15 games during the 2010 season with the Jacksonville Jaguars.
Detroit has also confirmed it acquired wide receiver Mike Thomas from Jacksonville -- its opponent Sunday on the road -- for an undisclosed draft pick.