Bentley, the starting nickelback, was injured on the team's second defensive series against the Giants.
The Lions selected Bentley in the third round of the 2012 draft. Injuries have limited his playing time in each of his first two seasons. In 2012, he played in just four games and had surgery on both shoulders. Last season he played in 13 games.
The Lions open their road schedule on Sunday against the Carolina Panthers.
- Paul Palladino