Williams had been sitting out with a sore foot, and eventually left the Bills training camp facility at St. John's Fisher College to see a doctor on his own.
The exact nature of the injury is still unclear. Buffalo head coach Doug Marrone was frustrated with reporters when continually asked about the nature and severity of Williams' injury.
Buffalo signed Williams before the 2012 season to the largest deal in NFL history for a defensive player of six years and $96 million. After a slow start, Williams regained his old form and finished with 10.5 sacks, tops on the team.