ORCHARD PARK, N.Y. -- Buffalo Bills starting defensive end Mark Anderson could miss another three weeks after having a setback recovering from left knee surgery.

Coach Chan Gailey said Monday that team doctors haven't ruled out Anderson requiring what he called another "procedure." If that happens, Gailey said Anderson would miss about three weeks.

Anderson has already missed three games since being hurt in a 45-3 loss at San Francisco on Oct. 7.

Gailey said starting cornerback Aaron Williams will miss a few weeks after hurting his right knee a day earlier in a 21-9 loss at Houston. Gailey said the injury is not as bad as initially feared.

Receiver Stevie Johnson is expected to play at New England on Sunday after he came up limping after hurting his right leg against the Texans.