Bills coach Doug Marrone didn't seem to have much information about the injury, which he became aware of Sunday night.
"He's going to be evaluated by our doctors, so he's off campus being evaluated," Marrone said Monday, according to The Buffalo News. "I have not heard any report yet."
"His foot was sore," Marrone said. "We're not going to make any mistakes about it. We're going to make sure that everything's fine. Our doctors are evaluating him. Where he is or where he goes, I'm not going to talk about that."
Williams -- entering the second year of his massive $96 million contract -- is expected to be a huge piece of Mike Pettine's hybrid defense in Buffalo. Pettine said this spring the team planned to move Williams all over the field in an effort "to get the bull's-eye off him."
Pettine's aggressive philosophy would seem to bode well for Williams having a big season. But he'll have to get back on the field first.