‘The Bills’ already suspect offensive line depth will be put to a stiff test this weekend in Chicago. Former Bears guard Chris Villarrial suffered a high right ankle sprain early in the second half blocking on a goal-line play and did not return. X-Rays were negative but he left the locker room wearing a large protective boot. Such injuries can take up to 4-6 weeks to heal, but coach Dick Juaron did not have a long-term prognosis on Monday. Villarrial was replaced in the lineup at right guard by second-year pro Duke Preston, who filled in for an injured Villarrial last season on several occasions and started one game.’