"It's crazy how it happened," Williams said after returning from an MRI that confirmed the sprain. "Literally, right when the ball was kicked and it went through the uprights, a guy fell on the back of my knee.
"It was just bad luck."
Kalil, who missed the final two preseason games with a sprained knee, played all 71 snaps with Williams sidelined and backup tackle Nate Chandler inactive with a knee injury.
Carolina coach Ron Rivera said Kalil got through the game without a setback. He said Amini Silatolu will figure into whatever mix the Panthers have as a backup tackle.
Williams said the knee is the same one he sprained three years ago at Oklahoma. He was out four to six weeks with that injury, which he described as worse.