Bills defensive end Mario Williams could be done in Buffalo.

Williams, who's sack total is down significantly this season, has been vocal about his concerns with the Bills' defensive scheme, and is among those on the team that miss former defensive coordinator Jim Schwartz, according to NFL Network's Ian Rapoport.

The 30-year-old has two years remaining on his six-year, $96-million deal, and Rapoport reports that it wouldn't be a surprise to see him hit the free-agent market in 2016. Releasing him would save the Bills $12.9 million against the cap.

There's a "clear, fundamental disconnect" between head coach Rex Ryan and the defensive line, and Williams seems to be the one at the heart of the problem, Rapoport reports.

Additionally, ESPN's Adam Schefter reports that Williams missed a team meeting this past week and told the Bills he was sick, but not everyone believed it.

In 12 games this season, Williams has four sacks and 16 tackles.