Marcell Dareus is facing a four-game suspension for another violation of the NFL's substance abuse policy.

Dareus was suspended one game last year for a violation of the league's substance abuse policy.

The Bills already are without rookie pass rusher Shaq Lawson, who is expected to miss at least the first month of the season after undergoing shoulder surgery, and rookie linebacker Reggie Ragland, who had season-ending knee surgery last week. Bills linebacker IK Enemkpali also will miss the season because of a knee injury.